A bushy or a climbing and branching, pubescent herbaceous perennial, often grown as an annual, up to 6 m tall, with a well-developed tap root with many laterals and well developed adventitious roots. Leaves alternate, trifoliolate, leaflets broadly ovate, 5Ð15 x 4Ð15 cm, entire, subglabrous or soft hairy. Inflorescences stiff axillary racemes with many flowers, peduncle 4Ð23 cm long, often compressed, glabrescent, rachis 2Ð24 cm long, flowers arising 1Ð5 together from tubercles on rachis, pedicels short, square, sparsely pubescent, flowers white, pink, red or purple, stamens diadelphous (9 + 1), ovary sessile, 10 mm long, finely pubescent, style abruptly upturned, 8 mm long, stigma capitate, glandular. Pods variable in shape and colour, flat or inflated, 5-20 x 1Ð5 cm, straight or curved, usually with 3Ð6 ovoid seeds of varying colour and size.;Other Botanical Information;The variability of lablab is great: many cultivars exist, and many subclassifications of the species can be found in the literature. Some distinguish subspecies, others varieties. For cultivated plants, the distinction of cultivar groups seems most appropriate.
C. imbricatus is a coarse, rhizomatous perennial, 70-150 cm tall;rhizomes short, 1-3 cm long, 5-10 mm thick, hardened;roots coarse. Culms erect, trigonous, often subtriquetrous distally, firm, coarsely ribbed, smooth, 3.5 -10 mm wide, sheathing bases 1-3 cm wide. Leaves 3-7;sheaths eligulate, spongy-thickened and purple-black proximately, fading to brown streaked with black distally;ligule absent;blades linear, folded to V shaped proximally, plicate distally, 35-90 cm ? 4-15 (-18) mm, with numerous cross veinlets, scabrous on the margins, abaxial mid-vein, and adaxial lateral veins, long-attenuate to triquetrous apex. Inflorescence a compound umbel-like corymb with ascending rays, 12-30 ?14-30 (-40) cm;involucral bracts 5-10, leaf-like, spreading, ascending to horizontal, the lowermost to 90 cm long;rays 6-12, to 25 cm long;spikes linear-cylindric, 1-6 (-8) cm ? 3-10 (-15) mm, in subradiate groups of (1-) 3-20 at ray tips, with (20-) 30-130 (-160) densely disposed spikelet, compressed, often slightly twisted, 3-6 ? 1-1.4 mm, acute to obtuse at apex, obtuse at base, with 8-22 florets. Stamens 3, the anthers 0.2 - 0.5 mm long, apiculate;styles 3-branched. Achene trigonous, dorsi-ventrally compressed, with the adaxial face plane and the abaxial faces broadly rounded, ellipsoid to ellipsoid-obovoid, 0.5-0.6 ?0.3-0.4 mm, very finely puncticulate to essentially smooth and glossy at maturity, dull whitish to stramineous (Acevedo-Rodr’guez and Strong, 2005).
C. imbricatus is a common weed in rice plantations and banana fields in tropical and temperate Asia (Mangoensoekardjo and Pancho, 1975;Soerjani et al., 1987;Noda et al., 1994;Li, 1998;Koo et al., 2000).
R. oleracea grows up to 40 m tall, with a distinctive, solitary, light gray, erect, cylindrical trunk up to 22 m. Its appearance has been described to be like a marble column (Zona, 1996). Leaves are in the crown at the top of the stem. Flowers are borne in large stalked panicles revealed when the leaf-sheaths beneath them drop off;abundant blue-violet fruit are small, obovoid and without stalks. The fruits turn purplish-black when ripe (Palmpedia, 2014). The roots can often be seen emerging from the stem just above the soil level. Individual trees have 16-22 or 20-22 leaves, 3-5 m long with leaflets of about 1 m in two horizontal ranks;leafstalks about 1.5 m long, broadening to surround and sheath stem Leaf segments are arrayed in two planes on either side of the rachis, however, in the past there was some disagreement in the literature on this characteristic. The species is noteworthy and relatively easy to identify for several reasons, one being that the leaves of the crown typically do not hang much below the horizontal, unlike other species in which the leaves droop and obscure the shaft of the crown. The species is also distinguished within its genus for an unopened peduncular bract which is strongly clavate with an acuminate tip. Groups of rachillae are undulate, forming wavy curves with amplitudes of 4 cm or more (Zona, 1996).
A. quinata is a liana, a vigorous, woody, deciduous, climbing vine. The stems are greyish brown, slender and cylindrical with small, prominent lenticels that have the shape of a flat ring or disk. Its pale red-brown winter buds' outer scales overlap like roof tiles. The petiole is slender (4.5Ð10 cm);its petiolules are slender (0.8Ð1.5(Ð2.5) cm). The leaves have several leaflets (typically 5Ð7) whose midribs all radiate from one point. The leaves alternate along the stems or cluster on the branchlets and are divided into five, or sometimes three to four or up to seven leaflets. The papery leaflets are obovate to obovate-elliptic. The leaflets are abaxially glaucous (whitish underneath), adaxially dark green (dark green above) with bases which are rounded to broadly cuneate. The apex, that is the point furthest from the point of attachment, is rounded and usually emarginated (notched) or cuspidate (with a point). The lateral leaflets measure 2Ð5 x 1.5Ð2.5 cm, while the terminal leaflets are 2.5Ð5(Ð7) cm. The racemes are clustered or bundled together measuring 6Ð12 cm. The scaly bracts are arranged like roof tiles. The stem that attaches or supports single flowers to the main stem of the inflorescence is approximately 2.5 cm and is located on short branches. The small, purple-brown, hanging flowers are held in groups of two to five and have somewhat fragrant chocolate or, in some sources, vanilla scent.
Uredinia hypophyllous, small, round or irregularly round, yellowish;urediniospores ellipsoid to broadly obovate, 20-33 x 18-24 µm, yellowish to hyaline, echinulate, germ pores three to four. Telia epiphyllous, numerous in circinating groups, round or irregularly-round, 2-4 mm diameter, white;teliospores irregularly fusiform, 34-45 x 12-19 µm, walls 1 µm thick, hyaline, pedicels short, hyaline, often deciduous. See Arthur (1912) (as Spirechina rubi) for a more detailed description.
Herbaceous vine, twining, attaining 5-6 m in length. Stems obtuse-pentagonal or cylindrical, puberulent. Leaves alternate, trifoliolate;leaflets chartaceous, the apex acute or short-acuminate, the margins sinuate;upper surface dark green, dull, glabrous, with slightly prominent venation;lower surface pale green or glaucous, glabrous, with the primary and secondary venation prominent;terminal leaflet 5.5-11 ? 3.5-7.5 cm, rhombic or deltate, the base cuneate or truncate;lateral leaflets asymmetrically deltate, the base truncate;petiolules thickened, 3-5 mm long, pubescent;rachis 1.5-2.5 cm long;petioles 6.5-9 cm long, sulcate, puberulent, the base slightly broadened. Inflorescences of axillary pseudoracemes, erect, 3-30 cm long, the flowers in groups of 2 per node of the inflorescence;pedicels 6-9 mm long, pilose;bracteoles minute, oblong. Calyx 2-2.5 mm long, green, campanulate, pilose, the sepals deltate, subequal;corolla white or lilac, pink or bluish, the standard semicircular, 7-10 mm long, abaxially pilose, the wings obovate, unguiculate, as long as the standard, the keel spirally twisted, ca. 1 cm long;stamens 10, diadelphous, the vexillar stamen broadened at the base;ovary with hispidulous pubescence, intermingled with uncinate hairs. Fruit an oblong-falcate legume or in the form of a half-moon, flattened, 5-7 ? 1-2 cm, puberulent with uncinate hairs or glabrescent, dehiscent by valves that open in a spiral containing 2Ð4 seeds. Seeds reniform, flattened, approximately 7 mm long, reddish brown, with dark spots (Acevedo-Rodr’guez, 2005).
Uredinia hypophyllous (on lower side of leaf), usually closely grouped or diffuse, in pale-yellowish spots, minute, usually less than 100 µm diameter, yellowish when dry;paraphyses incurved, hyaline or nearly so, one-septate near base, borne on basal cells with urediniospores, wall 3-5 µm thick on convex side, 1 µm on concave side;urediniospores ovoid, obovoid, or ellipsoid, 16-25 x 21-31 µm;wall 1.0-1.5 µm thick, hyaline or pale-yellowish, echinulate, pores obscure, but probably three, equatorial and located in angles. Telia hypophyllous, gregarious or scattered, round, pulvinate, 0.17-0.25 mm diameter, white, erumpent through stoma, with incurved, hyaline, thick-walled paraphyses at outer part;teliospores and paraphyses formed superficially at one apex of a single or usually a bundle of sporogenous hyphae;teliospores ovoid or ellipsoid, thin-walled, less than 1 µm thick, hyaline, usually slightly attenuated at apex or rounded at both ends, 26-41 x 11-16 µm, forming a cylindrical four-celled promycelium;pericel short, fragile, hyaline;paraphyses cylindrical, hyaline, strongly incurved, thick-walled, 33-51 x 8-9 µm. See Tai (1947) and Cummins (1950) for more detailed descriptions.
X. citri is a Gram-negative, straight, rod-shaped bacterium measuring 1.5-2.0 x 0.5-0.75 µm. It is motile by means of a single, polar flagellum. It shares many physiological and biochemical properties with other members of the genus Xanthomonas. It is chemoorganotrophic and obligately aerobic with the oxidative metabolism of glucose. Colonies are formed on nutrient agar plates containing glucose and are creamy-yellow with copious slime. The yellow pigment is xanthomonadin. Catalase is positive, but Kovacs' oxidase is negative or weak;nitrate reduction is negative. Asparagine is not used as a sole source of carbon and nitrogen simultaneously;various carbohydrates and organic acids are used as a sole source of carbon. Hydrolysis of starch, casein, Tween 80 and aesculin is positive. Gelatine and pectate gel are liquefied. Growth requires methionine or cysteine and is inhibited by 0.02% triphenyltetrazolium chloride. Biovars may be distinguished by utilization of mannitol. For further information on the bacteriological properties of X. citri, see Goto (1992).
Strains of groups B, C and D have many properties in common with group A, the differences being detected by the utilization of only a few carbohydrates (Goto et al., 1980).
Features of citrus-attacking xanthomonads including X. citri and the genus Xanthomonas as a whole, have been characterized at the molecular level for the development of quick and accurate methods for reclassification and identification. The procedures include DNA-DNA hybridization (Vauterin et al., 1995), genomic fingerprinting (Lazo et al., 1987), fatty acid profiling (Yang et al., 1993), SDS-PAGE (Vauterin et al., 1991) and isoenzyme profiles (Kubicek et al., 1989) and monoclonal antibodies (Alverez et al., 1991).
Phage-typing is applicable to X. citri with greater reliability than any other plant pathogenic bacterium investigated so far. Many strains of X. citri are lysogenic (Okabe, 1961). Two virulent phages, Cp1 and Cp2, can infect 98% of the strains isolated in Japan (Wakimoto 1967). Similar results were also obtained in Taiwan (Wu et al., 1993). The filamentous temperate phages and their molecular traits have been studied in detail (Kuo et al., 1994;Wu et al., 1996). Phage Cp3 is specific to the canker B strains (Goto et al., 1980). No phages specific to canker C and D strains have been isolated.
Methods of detecting X. citri from natural habitats include leaf-infiltration, bacteriophage, fluorescent antibody and ELISA (Goto, 1992). The polymerase chain reaction and dot blot immunobinding assay (DIA) were developed for rapid, sensitive, and specific detection of the pathogen. The detectable limits were reported to be around 30 c.f.u./ml for the former and 1000 c.f.u./ml for the latter (Hartung et al., 1993, 1996;Wang et al., 1997;Miyoshi et al., 1998).
Canker lesions begin as light yellow, raised, spongy eruptions on the surface of leaves, twigs and fruits. The lesions continuously enlarge from pin-point size over several months and can be of many different sizes based on the age of the lesion. As the lesions enlarge, the spongy eruptions begin to collapse, and brown depressions appear in their central portion, forming a crater-like appearance. The edges of the lesions remain raised above the surface of host tissue and the area around the raised portion of the lesion may have a greasy appearance. The lesions become surrounded by characteristic yellow halos. Canker lesions retain the erupted and spongy appearance under dry conditions, such as in a greenhouse;whereas they quickly enlarge and turn to flat lesions with a water-soaked appearance with frequent rain. Canker lesions vary in maximum size from 5 to 10 mm, depending on the susceptibility of the host plant. The symptoms are similar on leaves, fruit and stems.
Canker lesions are histologically characterized by the development of a large number of hypertrophic cells and a small number of hyperplastic cells. At an early stage of infection, the cells increase in size and the nuclei and nucleoids stain more easily;there is also an increase in the amount of cytoplasm synchronized with rapid enlargement. However, these hypertrophied cells do not divide;cell division is only detected in the peripheral areas of lesions adjacent to healthy tissue.
The lesions of canker B, C and D are similar in appearance and histology to those of canker A (Goto, 1992).
Reddy and Naidu (1986) reported canker lesions on roots;however, this has not been confirmed.
X. citri is a bacterial pathogen that causes citrus canker - a disease which results in heavy economic losses to the citrus industry worldwide either in terms of damage to trees (particularly reduced fruit production), reduced access to export markets, or the costs of its prevention and control. Lesions appear on leaves, twigs and fruit which cause defoliation, premature fruit abscission and blemished fruit, and can eventually kill the tree. It is introduced to new areas through the movement of infected citrus fruits and seedlings, and inadvertent re-introduction is highly likely despite the quarantine restrictions that are in place in many countries. Locally, X. citri is rapidly disseminated by rainwater running over the surfaces of lesions and splashing onto uninfected shoots;spread is therefore greatest under conditions of hight temperature, heavy rainfall and strong winds. Some areas of the world have eradicated citrus canker, others have on-going eradication programmes, however, this pathogen remains a threat to all citrus-growing regions.
The Citrus species listed in the table of hosts, and the following hybrids, are natural hosts of X. citri, with varying degrees of susceptibility to X. citri. In addition to host plant, susceptibility is also affected by the plant part affected, whether leaves, fruits or twigs. Reddy and Naidu (1986) reported canker lesions on roots but this has not been confirmed.
C. aurantiifolia x Microcitrus australasica (Faustrime), C. limon x M. australasica (Faustrimon), C. madurensis x M. australasica (Faustrimedin), C. sinensis x Poncirus trifoliata (Citrange), C. paradisi x P. trifoliata (Citrumelo) (Schoulties et al., 1987), C. aurantifolium x P. trifoliata (Citradia), C. nobilis x P. trifoliata (Citrandin), C. unshiu x P. trifoliata (Citrunshu), Citrange x P. trifoliata (Cicitrangle), C. adurensis x Citrange (Citrangedin), C. deliciosa x Citrange (Citrangarin), C. unshiu x Citrange (Citranguma), Fortunella margarita x Citrange (Citrangequat), F. japonica x C. aurantiifolia (Limequat), C. maxima x C. aurantiifolia (Limelo), C. madurensis x C. aurantiifolia (Bigaraldin), C. maxima x C. sinensis (Orangelo), F. margarita x C. sinensis (Orangequat), C. nobilis (Clementine) x C. maxima (Clemelo), C. nobilis (King of Siam) x C. maxima (Siamelo), C. unshiu x C. maxima (Satsumelo), C. deliciosa x C. maxima (Tangelo), C. nobilis (King of Siam) x C. sinensis (Siamor), C. deliciosa x C. madurensis (Calarin), C. unshiu x C. madurensis (Calashu). C. aurantiifolia x F. marginata is immune (Reddy, 1997).
Other than Citrus species and their hybrids, most plants, except P. trifoliata, are not sufficiently susceptible to X. citri under natural conditions to warrant attention as hosts of the bacterium. Although the potential of these plants as natural hosts seems to be negligible, further investigation is necessary because no confirmative host surveys have been undertaken since the 1920s. Species names within the genus Citrus also merit some attention due to their inconsistent use by authors.
Plants other than Citrus spp.:
Unless otherwise stated, the following plants refer to Peltier and Frederich (1920, 1924) who defined susceptibility on the basis of artificial inoculation in the greenhouse (G) and/or in the field (F): Aeglopsis chevalieri (G), Atalantia ceylonica (G), Atalantia citrioides (G), Atalantia disticha (G) (Lee, 1918), Chalcas exotica (G), Casimiroa edulis (G, F), Chaetospermum glutinosum (G, F), Clausena lansium (G), Citropsis schweinfurthii (G), Eremocitrus glauca (G, F), Evodia latifolia (G), Evodia ridleyei (G), Feronia limonia [ Limonia acidissima ] (G), Feroniella lucida (G, F), Feroniella crassifolia (G), Fortunella hindsii (G, F), Fortunella japonica (G, F), Fortunella margarita (G, F), Hesperethusa crenulata (G, F), Lansium domesticum (G), Melicope triphylla (G), Microcitrus australasica (G, F), Microcitrus australasica var. sanguinea (G, F), Microcitrus australis (G, F), Microcitrus garrowayi (G, F), Paramignya monophylla (G), Paramignya longipedunculata (G) (Lee, 1918), Poncirus trifoliata (G, F), Xanthoxylum clava-herculis [ Zanthoxylum clava-herculis ] (G, F), Xanthoxylum fagara [ Zanthoxylum fagara ] (G, F) (Jehle, 1917). Atalantia ceylanica, A. monophylla, Microcitrus australis, Feronia limonia and Severinia buxifolia are immune (Reddy, 1997). In India, goat weed (Ageratum conyzoides) is reported to be a host (Pabitra et al., 1997) but confirmation is needed.
The following plants have also been reported as susceptible to X. citri, however, the original descriptions were either not confirmed (U) or contradict those of other authors (C): Aegle malmelos (C), Balsamocitrus paniculata (U), Feroniella obligata (U), Matthiola incana var. annua (U) and Toddalia asiatica (C).
Of the primary hosts listed, yuzu is highly resistant (Goto, 1992) and calamondins, Cleopatra mandarin and Sunki mandarin are immune (Reddy, 1997). Both Fortunella japonica and F. margarita are highly resistant (Goto, 1992).
R. solanacearum is a Gram-negative bacterium with rod-shaped cells, 0.5-1.5 µm in length, with a single, polar flagellum. The positive staining reaction for poly-ß-hydroxybutyrate granules with Sudan Black B or Nile Blue distinguishes R. solanacearum from many other (phytopathogenic) Gram-negative bacterial species. Gram-negative rods with a polar tuft of flagella, non-fluorescent but diffusible brown pigment often produced. Polyhydroxybutyrate (PHB) is accumulated as cellular reserve and can be detected by Sudan Black staining on nutrient-rich media or the Nile Blue test, also in smears from infected tissues (Anonymous, 1998;2006) On the general nutrient media, virulent isolates of R. solanacearum develop pearly cream-white, flat, irregular and fluidal colonies often with characteristic whorls in the centre. Avirulent forms of R. solanacearum form small, round, non-fluidal, butyrous colonies which are entirely cream-white. On Kelman’s tetrazolium and SMSA media, the whorls are blood red in colour. Avirulent forms of R. solanacearum form small, round, non-fluidal, butyrous colonies which are entirely deep red.
The bacterium may be obtained from infected tubers or stems for staining purposes if a small portion of tissue is pressed onto a clean glass slide. Potato tubers can be visually checked for internal symptoms by cutting. Suspect tubers should be diagnosed in the laboratory. Appropriate laboratory methods to detect the pathogen have been laid down in a harmonized EU-interim scheme for detection of the brown rot bacterium (Anon., 1997). These methods are based on earlier described indirect immunofluorescence antibody staining (IFAS). Standard samples of 200 tubers per 25 t of potatoes are taken (Janse, 1988;OEPP/ EPPO, 1990a;Anon., 1997, 1998, 2006). Recently a very effective selective medium has been described (Engelbrecht, 1994, and modified by Elphinstone et al., 1996), that can also be applied for detection in environmental samples such as surface water, soil and waste (Janse et al., 1998;Wenneker et al., 1999). ELISA and PCR, based on 16S rRNA targeted primers as well as fluorescent in-situ hybridization (FISH) using 16S and 23S rRNA-targeted probes have also been used.
Ralstonia syzygii, causal agent of Sumatra disease of clove (Syzygium) and the distinct Blood Disease Bacterium, causal agent of blood disease of banana in Indonesia, are closely related to R. solanacearum and cross-react in serological and DNA-based detection methods (Wullings et al., 1998;Thwaites et al., 1999).
Foliage: the first visible symptom is a wilting of the leaves at the ends of the branches during the heat of the day with recovery at night. As the disease develops, a streaky brown discoloration of the stem may be observed on stems 2.5 cm or more above the soil line, and the leaves develop a bronze tint. Epinasty of the petioles may occur. Subsequently, plants fail to recover and die. A white, slimy mass of bacteria exudes from vascular bundles when broken or cut.
Tubers: external symptoms may or may not be visible, depending on the state of development of the disease. Bacterial ooze often emerges from the eyes and stem-end attachment of infected tubers. When this bacterial exudate dries, soil masses adhere to the tubers giving affected tubers a 'smutty' appearance. Cutting the diseased tuber will reveal browning and necrosis of the vascular ring and in adjacent tissues. A creamy fluid exudate usually appears spontaneously on the vascular ring of the cut surface.
Atypical symptoms on potato (necrotic spots on the epidermis), possibly caused after lenticel infection, have been described by Rodrigues-Neto et al. (1984).
Symptoms of brown rot may be readily distinguished with those of ring rot caused by Clavibacter michiganensis subsp. sepedonicus (EPPO/ CABI, 1997). R. solanacearum can be distinguished by the bacterial ooze that often emerges from cut stems and from the eyes and stem-end attachment of infected tubers. If cut tissue is placed in water, threads of ooze are exuded. Because such threads are not formed by other pathogens of potato, this test is of presumptive diagnostic value. For ring rot, tubers must be squeezed to press out yellowish dissolved vascular tissue and bacterial slime.
The youngest leaves are the first to be affected and have a flaccid appearance, usually at the warmest time of day. Wilting of the whole plant may follow rapidly if environmental conditions are favourable for the pathogen. Under less favourable conditions, the disease develops slowly, stunting may occur and large numbers of adventitious roots are produced on the stem. The vascular tissues of the stem show a brown discoloration and drops of white or yellowish bacterial ooze may be released if the stem is cut (McCarter, 1991).
One of the distinctive symptoms is partial wilting and premature yellowing of leaves. Leaves on one side of the plant or even a half leaf may show wilting symptoms. This occurs because vascular infection may be restricted to limited sectors of stems and leaf petioles. In severe cases, leaves wilt rapidly without changing colour and stay attached to the stem. As in tomato, the vascular tissues show a brown discoloration when cut. The primary and secondary roots may become brown to black (Echandi, 1991).
On young and fast-growing plants, the youngest leaves turn pale green or yellow and collapse. Within a week all leaves may collapse. Young suckers may be blackened, stunted or twisted. The pseudostems show brown vascular discoloration (Hayward, 1983). Moko disease, caused by R. solanacearum, is easily confused with the disease caused by Fusarium oxysporum f.sp. cubense. A clear distinction is possible when fruits are affected - a brown and dry rot is only seen in Moko disease.
Seedling wilt manifests itself as yellowing of the mature lower leaves, which show scorching and browning of the tissue between the veins. The younger leaves and terminal shoot become flaccid and droop. Affected seedlings show either a gradual loss of leaf turgidity or sudden wilting. Seedling wilt becomes evident in the early hours of the day and gradually becomes more pronounced by midday, especially on sunny days. The wilted seedlings may partially recover during the afternoon and evening when temperatures fall, but wilting becomes more pronounced on successive days. The roots of affected seedlings exhibit a brownish-black discoloration. In advanced stages of disease, the tuberous portion of the root becomes discoloured and spongy. In due course, seedlings with pronounced wilt symptoms become completely desiccated.
In container nurseries, R. solanacearum infects the cotyledons of emerging seedlings causing greyish-brown, water-soaked lesions, which spread to the entire cotyledon and become necrotic. The infection spreads to the adjoining stem and root tissues and the affected seedlings rot and die. Collar rot appears in 1- to 4-month-old bare-root seedlings as greyish-brown, water-soaked lesions at the collar region of seedlings, just above the soil level. The lesions spread longitudinally on the stem, both above and below ground level, becoming sunken and necrotic. The younger leaves become flaccid and droop followed by leaf scorching and pronounced vascular wilt. In bare-root nurseries, wilt usually occurs in small patches affecting individuals or groups of seedlings, which expand as more seedlings succumb to the infection.
Infection of mature foliage begins as greyish-brown to greyish-black, irregular lesions that spread to the entire leaf lamina. Infection spreads to the petioles and stems.
The strains in the race 3 group are a select agent under the US Agricultural Bioterrorism Protection Act of 2002 (USDA, 2005). Peculiarly, the organism, if not yet already present in North America in pelargonium (Strider et al., 1981), was introduced with cuttings of this host by American companies producing these cuttings for their markets in countries like Kenya and Guatamala (Norman et al., 1999, 2009;Kim et al., 2002;Williamson et al., 2002;Williamson et al., 2002;O’ Hern, 2004). A similar situation led to introductions of the pathogen from Kenya into some northern European nurseries. Once the source (contaminated surface water) was recognized and proper control measures (use of deep soil water, disinfection of cutting producing premises and replacement of mother stock), the problem was solved and the disease in greenhouses eradicated (Janse et al., 2004);Similarly race 1 has been introduced into greenhouses with ornamental plants (rhizomes, cuttings or fully grown plants) such as Epipremnum, Anthurium, Curcuma spp. and Begonia eliator from tropical areas (Norman and Yuen, 1998, 1999;Janse et al., 2006;Janse, 2012). Introduction can and did occur from Costa Rica and the Caribbean, Indonesia, Thailand and South Africa. However, this idea of placing pathogens on bioterrorist list for unclear and perhaps industry-driven reasons and its effects, is strongly opposed in a recent publication from leading phytobacteriologists. This is because R. solanacearum is an endemic pathogen, causing endemic disease in most parts of its geographic occurrence, moreover normal quarantine regulations are already in place where the disease is not present or only sporadically and are thought to be more efficient and less damaging to trade and research than placing this pathogen on select agent lists and treating it as such (Young et al., 2008). Peculiarly, it has been used in the control of a real invasive species, the weed kahili ginger (Hedychium gardenarium) in tropical forests in Hawaii. This is not without risks because strains occurring on this weed host were thought to be non-virulent, but later appeared to be virulent on many edible and ornamental ginger species as well (Anderson and Gardner, 1999;Paret et al., 2008). The earlier mentioned tropical strains belonging to phylotype II/4 NPB could become an emerging problem not only in the Caribbean, but also to Southern Europe and North Africa where higher yearly temperatures prevail. Another threat for these countries could be strains belonging to race 1, biovar 1 (phylotype I) that have already been reported from field-grown potatoes in Portugal (Cruz et al., 2008).
R. solanacearum as a species has an extremely wide host range, but different pathogenic varieties (races) within the species may show more restricted host ranges. Over 200 species, especially tropical and subtropical crops, are susceptible to one or other of the races of R. solanacearum. Worldwide, the most important are: tomato, tobacco, aubergine, potato, banana, plantain and Heliconia. Within the EPPO region, race 3 (see Biology and Ecology) with a limited host range including potato, tomato and the weed Solanum dulcamara, is considered to have potential for spread.
Other host crops are: Anthurium spp., groundnut, Capsicum annuum, cotton, rubber, sweet potato, cassava, castor bean and ginger.
Many weeds are alternative hosts of the pathogen. Solanum cinereum in Australia (Graham and Lloyd, 1978), Solanum nigrum and, in rare cases, Galinsoga parviflora, G. ciliata, Polygonum capitata, Portulaca oleracea (for example, in Nepal;Pradhanang and Elphinstone, 1996a) and Urtica dioica have been reported as weed hosts for race 3 (Wenneker et al., 1998). S. nigrum and S. dulcamara are primary wild hosts for race 3.
Lists of host records have been recorded (Kelman, 1953;Bradbury, 1986;Persley, 1986;Hayward, 1994a) but the original reports, gathered over many years, vary greatly in reliability. Few reference strains from reported host plants have been deposited in publicly accessible culture collections to support the authenticity of records.
The mycelium of S. rayssiae var. zeae permeates the mesophyll;the hyphae are irregular in shape and are lobulate rather than tubular. Sporangia are produced sympodially in groups of between two and six in a basipetal succession on sporangiophores, which arise from hyphae congregated in the substomatal cavities;sporangial production occurs superstomatally.
The characteristic feature of brown stripe downy mildew, as its name suggests, is the vein-limited striping of the foliage. Other parts of the plant including husk leaves, ears or tassels, do not show symptoms even though all of the leaves including the flag leaf may be affected by the disease.
Sori in swollen ovaries, ovoid to short cylindrical, 3-5 mm long, partly hidden by parts of floret. Spore masses covered by pale-brown peridium that ruptures irregularly, usually at apex, exposing blackish-brown, semi-agglutinated to powdery masses surrounding short, tapering columella composed of plant and fungus tissue. Spores initially aggregated in very loose spore balls, 25-30 µm diameter;spores single-celled, globose, subglobose, or ovoid to slightly irregular (8-)9-12 x 9.5-13(-14) µm, yellowish-brown;wall 0.5 µ m thick, finely and densely echinulate, spore profile appearing finely toothed. Areas between spines finely, densely warty. Sterile cells colourless, smooth, in irregular groups among spores, somewhat larger than spores;walls 1 m m thick. Spores germinate to produce a short, transversely segmented basidium, each of the four cells producing one colourless thin-walled spore. Spores infect ovaries in grass florets. For additional information see Vánky (2007).
The fungus occurs in the individual florets only, as small dark bodies replacing the ovary/seed. Individual spores mixed with the seed or adhering to stems could only be detected and identified using high magnification light microscopy.
There is little published information on this plant pathogenic fungus, which has a limited geographic distribution. As hosts exist in other regions of the world with similar environmental conditions, this species may pose a threat to native or agricultural plants if introduced.
In addition to the host plants listed, hybrids of Saccharum are also affected.
B. pilosa seedlings have lanceolate (strap-shaped) cotyledons, 25 mm long, and purple-tinged hypocotyls. The first true leaf is similar to later leaves. Finot et al. (1996) describe the morphology of dry seed, unfolded cotyledons, first true leaf or leaf pair unfolded and two to five true leaves unfolded. Original drawings and photographs accompany each description.
The plant is an erect annual herb, 20–150 cm tall (in tall plants sometimes the branches straggling), very variable, reproducing by seeds. Main root pivotant. Stems square, glabrous or minutely hairy, green or with brown strips. Dark green, opposite leaves on stems and branches, 4–20 cm long, up to 6 cm wide, the lower leaves simple, ovate and serrate, the upper leaves trifoliolate or imparipinnate with 2–3 pairs of pinnae and a single terminal leaflet. Petioles are 2–5 cm long.
The inflorescence is an isolated or grouped pedunculated capitula, emerging from the leaf axil. Heads borne singly at the ends of long, slender, nearly leafless branches;narrow, discoid, the disk 4-6 mm wide at anthesis;ray florets, absent or 4–7 per head, white or pale-yellow, 2–8 mm long, disk florets, 35–75 per head, yellow.
Achenes (commonly referred to as 'seeds') linear, black or dark brown, 1–1.5 cm long, flat, 4-angled, sparsely hairy. Pappus with 2–3(–5) yellowish barbed awns, 1–2 mm long. The achenes are the dispersal units;dispersion is aided by the awns as they readily attach to animal skin, machinery and clothing.
B. pilosa is troublesome in both field and plantation crops and is reported to be a weed of 31 crops in more than 40 countries (Holm et al., 1977).
It is regarded as a principal weed of sugarcane, maize, coffee, tea, cotton, potatoes, vegetables, bananas, beans and citrus in various Latin American and African countries (Holm et al., 1977) and a serious weed in many other situations. In upland rice in South and South-East Asia, it is common in Thailand and present in Indonesia, Laos, Myanmar, Philippines and Vietnam (Galinato et al., 1999).
Plants: perennial, heterosporous herbs, free floating, with microspores and megaspores produced on the same plant, green, up to 30 cm long, 5 cm wide, mat-forming, mat to 2.5 cm thick (or much thicker, depending on local conditions such as water current, waves, etc.);roots absent;stems irregularly branched, pubescent.
Leaves: short petiolate, in whorls of three, two upper and one lower;upper leaves floating, photosynthetic, entire, elliptic-ovate to rounded, with a distinct midvein, aerolate, 0.7-3 cm long, to 1.8 cm wide, apices rounded to emarginate, the aerolae either fairly uniform in size throughout, or inner longer than outer;papillae apex split into several hairs that form a birdcage-like structure which traps an air bubble when submerged, creating a non-wettable upper surface;leaves often folded in half under crowded growth conditions;lower leaves subsessile or petiolate, with or without sporocarps attached, 1.5-2.0 cm long, to 0.5 cm wide, the petiole to 3 cm long, submersed, non-photosynthetic, finely divided into linear segments (feathery), segments appearing as and functioning as roots.
Sporocarps (when present): pubescent, sessile to long-stalked, globose to ovoid, rounded to apiculate at apex, either clustered at apex of submersed leaf or arising alternately in two rows down the length of the submersed leaf similar in size, sessile or stalked, in clusters or rows on lower leaves, the sporocarp wall a modified indusium;microsporocarps inconspicuous, globular, with an internal short column, the columns basal, bearing many microsporangia;microspores minute;megasporocarps inconspicuous, globular, with many megasporangia.
Microsporangia: stalked, with one massula (group of microspores);massulae with 64 microspores.
Megasporangia: sessile, with one megaspore;megaspores to 2 mm long.
Within the S. auriculata complex, to which S. molesta belongs, all of the species are very similar in their vegetative morphology. Therefore, reproductive structures should be used for identifying species within the complex whenever possible, though plants bearing sporocarps are rarely reported in the United States (Riefner and Smith, 2009). A comparison of species within the complex is provided in the section Similarities to Other Species/Conditions.
S. molesta is a free-floating aquatic plant native to south-eastern Brazil. It has been spread widely throughout the world during the past 50 years and is invasive in a variety of aquatic habitats, including lakes, rivers and rice paddies. Based on the environmental, economic and human health impacts, S. molesta ranks a close second behind water hyacinth on a list of the world's most noxious aquatic weeds. It has also been recently added onto the list of the world’s 100 most invasive species.
The morphology of adult females was described in detail by Ezzat and McConnell (1956), McKenzie (1967), Entwistle (1972), Cox (1989), Cox and Freeston (1985) and Padi (1990).
The external diagnostic characters include 18 pairs of short, stout wax filaments along margins, of which the anal and two preceding pairs are slightly longer than the rest but less than 20% of body length. Dorsum covered with fine mealy wax with a slightly darker, longitudinal, median stripe from first thoracic to mid-abdominal segments. Body colour beneath wax is usually yellow to peach pink. Antenna 8 segmented. Authoritative identification requires microscopic study of slide-mounted females;Sirisena et al. (2013) provided a method for preparation of slide mounts of adult females.
Body of slide-mounted adult female oval, 1.6-3.2 mm long, 1.2-2.0 mm wide (Cox, 1989). Body margin with 18 pairs of cerarii, each cerarius with two conical setae except for the pre-ocular pair which may have one or three setae each. Legs elongate;hind trochanter + femur 220-350 µm long;hind tibia + tarsus 260-420 µm long. Ratio of hind tibia + tarsus to hind trochanter + femur 1.1-1.3;translucent pores present on hind coxae and tibiae. Circulus quadrate, width 120-200 µm. Cisanal setae shorter than anal ring setae. Anal lobes moderately developed;anal lobe cerarii each situated on a small, moderately sclerotized area;venter of each anal lobe with sclerotized anal lobe bar bearing apical seta and bar seta.
Multilocular disc pores present around vulva, in single or double rows across posterior edges of abdominal segments III-VII, in single rows across anterior edges of segments V-VII, in marginal groups on abdominal segments IV-VII and sometimes a few pores scattered over median area of the thorax and head, but no more than a total of six pores behind the front coxae. Oral collar tubular ducts of two sizes: smaller ducts in sparse rows across median areas of abdominal segments I-VII;larger ducts in marginal groups of variable size around entire venter including head and thorax, and scattered over median area of thorax.
Multilocular disc pores absent. Tubular ducts without rims, slightly larger than the larger ducts on venter, often adjacent to some cerarii. One or two ducts sometimes present on median areas. Simple pores present of two sizes, smaller pores smaller than the smaller size on the venter, scattered over entire dorsum;larger simple pores, each about twice the size of a trilocular pore, present in small groups along mid-line of thoracic and anterior abdominal segments. Setae short and flagellate, longest seta on abdominal segments VI or VII 30-35 µm long.
Males each have a single pair of wings and no mouthparts. They cannot be authoritatively identified at present. Detailed descriptions of the morphology of the adult male are available in Giliomee (1961), Afifi (1968) and Afifi et al. (1976).
Although generally cryptic in nature, P. citri can be easily detected on fruits and inflorescences. On cocoa, it can be readily detected on the surface of pods, where it usually forms large colonies. Colonies in terminal buds, bases of leaf petioles, points of attachment of chupons [suckers], fruits and pods, and the bark of trees can be detected using a hand lens or, in the case of terminal buds, by teasing them apart and inspecting them under a dissecting microscope. On Citrus, the area underneath the calyx and the peduncle of the fruit provides a good hiding place (Meyerdirk et al., 1981). P. citri can also be detected in the field by the presence of ants and sooty moulds that develop on excreted honeydew (Gausman, 1974) and by wilt of plant parts such as leaves, inflorescences and fruits or berries.
P. citri feeding leads to general wilting due to sap depletion. On cocoa, flower stalks, buds and young pods are attacked (Entwistle, 1972). In Taiwan, infested immature coffee berries become deformed and drop to the ground (Moriyama, 1941).
P. citri infestation also causes indirect physical damage because sugary honeydew excreted by the mealybugs fouls plant surfaces, giving rise to sooty moulds (Gausman and Hart, 1974) that block light and air from the leaves, inhibiting photosynthesis.
Citrus mealybug is the second most important vector of several strains of Cacao swollen shoot virus;symptoms include leaf chlorosis, root necrosis, root and stem swellings and dieback (Posnette, 1941;Cotterell, 1943).
Planococcus citri is a highly polyphagous, adaptable mealybug that can feed on many host plants in a variety of conditions, and can reproduce rapidly. It has been reported on over 200 host-plant species belonging to 191 genera and 82 families, and can seriously damage many crops, particularly citrus and glasshouse tomatoes. It is known to transmit some plant virus diseases like Cacaoa swollen shoot virus. The mealybug is of Old World origin, but its polyphagy has facilitated its spread about the world by human transport of infested plants over many years, and it is now established in in all the temperate and tropical zoogeographic regions, and lives under glass in higher latitudes. Its small size and cryptic habits makes it difficult to detect and identify at plant quarantine inspection. The increase in international trade in fresh plant material in recent years is facilitating its continued spread.
P. citri is polyphagous and occurs on a wide range of flowering plants, having been recorded on over 200 host species belonging to 191 genera in 82 families (García et al., 2016).
In the tropics, it occurs mainly on the aerial parts of crops such as cocoa, bananas, tobacco and coffee and on wild trees such as Ceiba pentandra and Leucaena (Strickland, 1951a,b;Le Pelley, 1968;Entwistle, 1972). In Ghana, P. citri has been recorded on about 54 host plants, including cocoa, cola, pineapples, Musa paradisiaca and others within the families Bombacaceae, Euphorbiaceae, Fabaceae, Moraceae, Rubiaceae, Solanaceae, Sterculiaceae, Tiliaceae and Urticaceae (Strickland, 1951a;Padi et al., 1999). Hargreaves (1937) cited Anisophyllea laurina as an alternative food plant in Sierra Leone.
In the South Pacific region, P. citri has been recorded on 20 host plants, including Brassica, Ceiba, Citrus, cocoa, Cyrtosperma, Cucurbita, Gardenia, Inocarpus, Ipomoea, Leucaena, Morinda, Ocimum, Psidium, Pueraria and Solanum spp. (Williams and Watson, 1988). Its host plants in Australia include pumpkins in New South Wales;Clerodendrum, Coleus, Croton and Erythrina species in hothouses, and Ceratonia, Siliqua and Veronica species in the open in Adelaide (Brooks, 1957);and pineapples (Carter, 1942), Vitis vinifera and passionfruits in Queensland (Williams, 1973;Murray, 1978b).
In India, P. citri occurs on mandarin orange (Amitava Konar, 1998) and has been recorded for the first time on soyabean (Jadhav et al., 1996).
In temperate regions, P. citri mainly occurs on greenhouse plants such as Coleus, ferns and gardenias, but also occurs outdoors under summer conditions on Citrus, grapes, figs, taro, date palms and potatoes (Bivins and Deal, 1973;Gibson and Turner, 1977). It mainly attacks Citrus but not grapes in the Mediterranean region (Cox, 1989) and California. In the former Soviet Union, it occurs on over 20 species of plants, notably Citrus, figs and pomegranates (Niyazov, 1969). In Turkmenistan, pomegranates are most liable to heavy infestation. It occurs on Areca sp. and a wide range of greenhouse ornamental plants in Korea (Paik, 1972) and Bulgaria (Tsalev, 1970).
In Texas, USA, P. citri has been recorded on the milk vine Cynanchum unifarium [ Cynanchum racemosum var. unifarium ] (French and Reeve, 1978). Host plants in India include Macadamia ternifolia (Wysoki, 1977).
Brevipalpus is a large, widespread genus, including over 65 species of very small flat mites. They are divided into six groups according to the number of lateral setae in the posterior half of the body (hysterosoma), the number of sensory setae on tarsus II of the female and the number of terminal setae on the palpus (Baker and Tuttle, 1987).
The Chilean grape flat mite is included in the obovatus group, having six pairs of lateral hysterosomal setae (Baker and Tuttle, 1987) and one sensory cylindrical seta (solenidion) on tarsus II.
Body oval, 320-340 µm, body setae very short, dorsal setae 14 to 16 µm. Six pairs of short dorsolateral setae, of which five pairs are strictly hysterosomal and the sixth pair is humeral (Jeppson et al., 1975). The distal segment of the palpus has three setae and tarsus II has a single distal solenidion rod.
The main distinguishing character is the propodosoma, which is evenly reticulate. The latter character separates B. chilensis from Brevipalpus obovatus;this feature can be better seen under a phase contrast microscope.
The male is very similar to the female with respect to the above morphological features.
From laboratory pure cultures, it is confirmed that the main characters used in separation are the shapes of the first and second propodosomal setae and the final three hysterosomal pairs, which are oblong in shape, whereas all other dorsal setae are much shorter and setiform.
The dorsocentral setae are short and setiform;all others are oblong of denticulated margin.
Under field conditions, all Brevipalpus mites look very similar in colour, shape and size. They can be easily found in preferred host plants with the aid of a x15 magnification hand lens. Overwintering adult females should be searched for on the underside of leaves, the pedicel disk area of citrus (Citrus spp.) and kiwifruit (Actinidia deliciosa), grape (Vitis vinifera) bunches near the pedicel, and under the bark or petiole cavities in deciduous plants.
A diagnostic Lucid key to 19 species of Brevipalpus is available in Flat Mites of the World.
For quarantine inspection purposes, the grape bunches can be washed with detergents within a funnel system to convey the water down and inspect specimens in a collecting pan.
This species is commonly found throughout central Chile on a variety of cultivated hosts such as grapes (Vitis vinifera), lemons (Citrus limon), kiwifruits (Actinidia deliciosa), persimmons (Diospyros kaki), and various flowers and ornamentals. In terms of abundance, Ligustrum spp. (privet) is by far the most important host plant;another character that links B. chilensis with Brevipalpus obovatus (see 'Similarities to other species').
The oldest known mounted specimens kept at the University of Chile Agricultural Museum, Chile, were collected on wine grapes (V. vinifera) in Central Chile in 1909. All specimens were labeled 'Tetranychid mites'. In terms of economic damage and because of its quarantine connotation, table grapes, Citrus spp., chirimoya (Annona cherimola), banyan (Ficus indica [Ficus benghalensis]), kiwifruit (Actinidia deliciosa) and a few others are extremely important because several markets, namely USA and Mexico, require a zero tolerance fumigation. However, in terms of physiological damage to the host, the wine grape is still the most recurrent.
Small, limited mite populations can be found on carnations (Dianthus caryophyllus), Euonymus, snapdragon (Antirrhinum spp.), chrysanthemum (Chrysanthemum spp.), Vinca sp., Ampelopsis sp., and assorted broad-leaf plants, including pome fruits. Under laboratory or greenhouse conditions, potted beans and privet (Ligustrum) may yield high mite populations.
Cultures of the anamorph on potato sucrose agar (pH 6.5) are pale beige with sparse white mycelium;purple discoloration later develops, accompanied by dark bluish-black, discrete stromata, some of which represent ascomatal initials. Microconidia unicellular, allantoid, curved, 5-10 x 2.5-3 µm. Macroconidia fusoid, falcate, 2-3 septate, 20-25 x 4-5 µm. Chlamydospores oval to globose, smooth or roughened, 10-15 x 8-10 µm.
Ascomata perithecioid, violaceous, embedded, single or in groups, in dark purple stromata;globose with a flattened base, 200-400 x 180-300 µm. Asci cylindrical, thin-walled, shortly pedicellate, 90-110 x 7-9.5 µm with 8 monostichous ascospores. Ascospores hyaline to straw-coloured, fusoid, 1-3 septate, finely roughened, 12-14.5 x 4.5-6 µm (Booth and Waterston, 1964).
Fraselle (1950) described the disease symptoms fully on C. robusta in the Belgian Congo (formally Zaire and now Democratic Republic of Congo). First symptoms were described as generalized chlorosis of the leaves which became flaccid and curled. Leaves dry up, turn brown and very fragile, and abscise. The crowns of the dead trees are completely defoliated. The branches may turn black-brown or blackish, and dry up. The bark on the trunk is hypertrophied and has numerous vertical or spiral cracks which reveal blue-black streaks in the wood under the bark. In the roots, the black rot becomes moist. Infection may be general or partial. Van der Graaff and Peters (1978), describing the disease in C. arabica in Ethiopia, observed that dieback may start unilaterally and extend to the whole tree.
Internally, in the diseased wood, the main tracheids are heavily infected by mycelium. At the limit of spread, the tracheids alone are affected but where the infection is long established, the mycelium is found in the fibres surrounding the vessels and medullary rays (Fraselle, 1950). Wood parenchyma is rarely attacked but primary xylem and pith may be attacked. Tyloses develop and a yellow gum is observed (Fraselle, 1950). Such occlusion of the vessels leads to the characteristic wilting and desiccation of the foliage. Mycelium is rarely present in the bark, reaching only the cortical medullary rays but fungal reproductive structures (fruiting bodies) can sometime be observed on the outside of the bark at the base of infected trees.
Further details of symptoms can be seen in various chapters and plates in Flood (2009).
Fusarium xylarioides (teleomorph = G. xylarioides) has been reported to be pathogenic to cotton seedlings of IAC 20 cultivar under laboratory conditions;less so under glasshouse conditions (Pizzinatto and Menten, 1991). It has also been isolated from rotting tomatoes in Nigeria (Onesirosan and Fatunla, 1976) but this may be a misidentification.
A. yali-inficiens is a dark-brown to black mould causing dark ('chocolate') brown spots on Ya Li pear (Pyrus bretschneideri) fruit from China.
Other unidentified species of Alternaria cause diseases on Ya Li pear (Pyrus bretschneideri) fruit from China, and diseases could be due to infection by more than one species at a time. Infections were sometimes observed on fruit stems before they progressed to the body of the fruit (Roberts, 2005). If the symptoms described in this datasheet are observed, prompt and correct identification requires microscopic observation of conidiophores and conidia produced on the fruit and in pure culture under prescribed conditions (Simmons, 2007).
Sunken, dark-red to chocolate-brown lesions on fruit with concentric zones, sometimes obscured by sporulation, and even to irregular margins, often appearing at the stem end. Sporulation develops as clusters of whisker-like growth from groups of dark, subsurface cells, the clusters enlarging and merging to produce a dark velvety appearance. Lesions on the stems are sunken, shiny, and dark-brown to black (Roberts, 2005).
A. yali-inficiens is an asexually reproducing, filamentous fungus known only since its isolation in 2001 from infections on fruit of Ya Li pears (Pyrus bretschneideri), exported from a certain region of China. Although most species of Alternaria are air-disseminated, its ability to spread and establish in other temperate fruit-growing regions is not known. This fungus may pose a threat to native or agricultural plants if introduced. Some countries importing pear fruit from China have established regulatory precautions against it.
Uredinia hypophyllous, scattered or in small groups, minute, 0.3-0.7 mm diameter, yellow, pulverulent;paraphyses clavate, erect or incurved, wall uniformly thin, hyaline;urediniospores globose, sub-globose, obovate, broadly ellipsoid or obovoid, 16-26 x 12-20 µm;walls 0.8-1.8 µm thick, coarsely echinulate, pale-yellow. Telia hypophyllous, scattered or gregarious, minute, round or irregular, 0.1-0.3 mm diameter, pulverulent, black;teliospores cylindrical, 3(-4)-septate, 40-74 x 22-28 µm (49-85 x 21-35 fide Hiratsuka et al., 1992), rounded at apex, more or less constricted at the septa, walls 2.0-2.5 µm thick, brown, smooth, two to three germ pores in each cell;pedicels hyaline, persistent, 65 µm long. See Wei (1988) and Hiratsuka et al. (1992) for more detailed descriptions.
Uredinia hypophyllous, scattered or loosely grouped, minute, early exposed, somewhat pulverulent, pale-yellow;paraphyses numerous, cylindrical or clavate, 30-50 x 8-12 µm, incurved, walls smooth, hyaline, 1.0-1.5 µm thick;urediniospores irregularly globose, obovate to ellipsoid, 16-33 x 10-16 µm, minutely echinulate, hyaline, walls 1.5 µm thick. Telia hypophyllous, scattered, minute, early exposed, 0.1-0.2 mm diameter, pulverulent, black;teliospores cylindrical, 2-4-septate, 34-102 x 18-27 µm, slightly attenuated at base, more or less constricted at septa, with a pale-brown projecting papilla at apex, chestnut-brown or yellowish-brown, pedicels hyaline, up to 47 µm long. See Wei (1988) for a more detailed description.
Structurally, the Lemnaceae are the simplest of the flowering plants. The plants are not differentiated into stems and leaves;instead, the plants in the family have an undifferentiated leaf-like body commonly referred to as a frond. Fronds floating, 1 or 2-few, coherent in groups, obovate, flat to thickish (but not gibbous), 0.8-4 mm, 1-2 times as long as wide, margins entire and thin, usually pale green, shining, nearly always with a sharp ridge with white papillae;veins 1, sometimes indistinct, very rarely longer than extension of air spaces, not longer than 2/3 of distance between node and apex;with or without small papillae along midline;anthocyanin absent;largest air spaces much shorter than 0.3 mm;turions absent. Roots to 1.5 cm, tip rounded to pointed, one root per frond;sheath not winged. Stipes (stalks) white, small, often decaying. Flowers within membranous cup-like spathes (open on one side) inside budding pouches located on either side of the basal end. Ovaries 1-ovulate, utricular scale open on 1 side. Fruits 0.6-1 mm, not winged. Seeds with 12-15 distinct ribs (Landolt, 1980;Flora of North America, 2008;Armstrong, 2009).
L. minuta is a small free-floating plant, no more than 3 mm in length. It is widely distributed in southern and western North America and is also found in Central and South America. It occurs in lowland ditches, ponds, canals, streams and rivers, and more rarely it is found in lakes (Preston and Croft, 1997). It often forms dense mats on the surface of water, reducing the light penetration and gas exchange, often causing the disappearance of submersed aquatic plants. Outbreaks are usually limited in time and space and are favoured by eutrophication. L. minuta is introduced in Eurasia (Landolt 2000) and it was first recorded in western France in 1965. From there it has spread all over Europe as far as southern Russia and Greece. It is also present in Japan (e.g. Landolt, 1986). It is considered a casual alien by Global Compendium of Weeds (2007). In many areas it is a noxious weed, as in Belgium, and it is included in the watch list with moderate impact (Branquart et al., 2007).
S. minima is a deep-green, free-floating, rootless, aquatic fern (ISSG, 2006). Stems can be up to 6 cm and leaves are from 1-1.5 cm long and almost round to elliptic. They are obtuse or notched at the apex and round to heart-shaped at the base. The upward surfaces of the fronds are covered with stiff hairs, with four separated branches. The under surface of the leaves are brown and pubescent with slender and unbranched hairs (Flora of North America Editorial Committee, 1993). The stiff hairs on the fronds serve to trap air, thus providing buoyancy (Dickinson and Miller, 1998). Obscure veins are areolate and do not quite reach to the leaf edges. Sporocarps occur in groups of four to eight, with up to 25 megasporangia (Flora of North America Editorial Committee, 1993).
S. minima is free-floating, which makes it easier to identify than most submerged aquatic vegetation. Volunteer monitors should be trained on the identity and habit of this potential invader.
S. minima is a very productive free-floating, non-rooted aquatic fern native to South and Central America. It was introduced outside its native range in southern Florida, USA in 1926 (USGS, 2005). The plant is degrading wetland ecosystems in several states of the USA (Tipping and Center, 2005). S. minima has an extremely high reproductive potential;the plants can rapidly colonize bodies of water, forming thick mats that displace native species, impact water quality, impede recreational activities, and clog waterways and irrigation channels (Rayachhetry et al., 2002). S. minima is also resistant to desiccation, allowing it to be transported long distances out of water (ISSG, 2006). The species can act as an annual, dying back when temperatures decrease and causing harmful nutrient pulses and dissolved oxygen crashes (Dickinson and Miller, 1998).
S. minima is a highly competitive species with a very high growth rate. Colonies of S. minima can grow very densely, such that they shade light from valuable native submerged aquatic plant species (USACE-ERDC, 2002). Dense colonies can thus decrease local biodiversity and degrade the habitat (ISSG, 2006). The plant is also highly competitive among other free-floating species. A competition study specifically showed that S. minima had negative effects on the change in cover of the species Azolla caroliniana and Spirodela punctata (Dickinson and Miller, 1998). In Louisiana, USA native Lemna species were completely replaced by S. minima (ISSG, 2005).
Spermogonia and aecia unknown. Uredinia on abaxial leaf surface, scattered or aggregated in small groups on a lesion, subepidermal, becoming erumpent, surrounded by paraphyses. Paraphyses united at the base, strongly incurved, 21-43 µm long, wall 2.5-5.5 µm thick, both dorsally and ventrally;urediniospores obovoid, obovoid-ellipsoid or oblong-ellipsoid, 16-27 x 11-17 µm, wall 1.5 µm thick, almost colourless, evenly echinulate, with four or six germ pores in equatorial zone of the spore wall, rarely scattered. Telia also formed on the abaxial surface, crustose, orange-brown, becoming dark-brown to blackish-brown, often confluent, subepidermal, applanate;teliospores more or less randomly arranged in 3-4 layers, oblong or ellipsoid, angular, 13-28 x 6-15 µm, wall thin and colourless, upper wall 2 µm thick and pale-brown. Basidiospores reniform, 9.0-12.5. x 5.5-8.0 µm. For an additional description and illustration, see Ono (2000).
The undersides of Ampelopsis leaves should be examined for yellowish, powdery uredinia and/or crust-like, orange-brown to blackish-brown telia.
Similarities to Other Species/Conditions
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This fungus appears to be highly host-specific, being restricted to the genus Ampelopsis with only a few other possible hosts (Ono, 2000). Thus, correct identification of the host ensures the identification of this species within the genus Phakopsora.
P. ampelopsidis forms strongly incurved, evenly thick-walled (2.5-5.5 µm) paraphyses in the uredinium, subglobose to oblong teliospores randomly arranged (not in rows) and not with spores in the upper row longer, and kidney-shaped basidiospores, by which it can be distinguished from the morphologically similar Phakopsora vitis on Parthenocissus and Phakopsora euvitis on Vitis.
As currently defined (Ono, 2000), the rust fungus P. ampelopsidis is a pathogen of hosts in the genus Ampelopsis and perhaps in related genera in the Vitaceae, but not of the cultivated grapevine species of Vitis or the ornamental species in Parthenocissus. Plants in Ampelopsis occur in Asia from Japan to Turkey as well as in North America (USDA-ARS, 2009), but the rust is not known in Europe, and has not been reported on Ampelopsis in the Americas. Only in eastern Asia, where the medicinal uses of Ampelopsis species are being investigated (Kim et al., 2007;Zhang et al., 2008), is this rust a potential problem. It is most likely to be spread by aerial dispersal of urediniospores to nearer parts of Asia, where species in the host genus are distributed.
Spermogonia epiphyllous, aggregated in minute groups opposite aecia, indefinite, becoming fused, subcuticular, 25-30 mm diameter. Aecia hypophyllous, caeomoid, circular or annulate, up to 1 mm diameter, orange, paraphysate;a eciospores globose to broadly ellipsoid, 25-22 x 23-16 µm;wall hyaline, coarsely verrucose with broad shallow warts up to 3 µm diameter, 1.5-2.0 µm thick, pores obscure. Uredinia hypophyllous, irregularly scattered without spots or on small reddish, yellowish, brownish, or purplish spots, occasionally on larger purplish blotches, 0.1-0.3 mm diameter, yellowish, paraphysate;urediniospores obovoid to ellipsoid, 19-24 x 16-18 µm;wall hyaline, echinulate, spines 1-2 µm apart, 0.5 µm high, 1-2 µm thick, pores 2.5-4.0 µm diameter, obscure, paraphyses cylindric-clavate, incurved, 40-60 x 8-13 µm, wall thickened to 2-3 µm at apex. Telia scattered or aggregate, minute, round or irregular, black;t eliospores cylindric, not constricted at septa, apex rounded and with a blunt apiculus, up to 13-19 long x 5-7 µm wide, 3-6-septate, dimensions excluding apiculus: 3-septate 59-71 x 30-37 µm;4-septate 73-89 x 32-37 µm;5-septate 86-104 x 32-37 µm;6-septate 98-111 x 32-36 µm;wall sienna to dark umber-brown, verrucose, 4-5 µm thick, pores two to four in each cell;pedicels 75-160 µm long, 7-10 µm wide at neck, swollen below to 13-19 µm wide. See Wilson and Henderson (1966), Laundon and Rainbow (1969), and Petrova and Denchev (2004) for more detailed descriptions.
There is little published information on this plant pathogenic fungus, which has limited geographic distribution. As hosts exist in other regions of the world with similar environmental conditions, this species may pose a threat to native or agricultural plants if introduced.
Spermagonia epiphyllous in groups, minute;aecia hypophyllous, caeomoid, in groups, yellow;aeciospores subglobose, 17-29 x 14-22 µm, wall hyaline, echinulate, 1-2 µm thick. Telia hypophyllous, scattered or gregarious, minute, round or irregular, 0.2-0.4 mm diameter, pulverulent, black;teliospores cylindrical, 4-6(-10)-septate, 57-147 x 22-43 µm, apex round with hyaline papilla up to 5 µm, two to three germ pores in each cell, wall chestnut-brown, minutely and closely verrucose, 3-5 µm thick;pedicels hyaline, up to 60 x 19 µm. See Ragunathan and Ramakrishnan (1973) for a more detailed description.
This rust attacks species of Rosa native to Asia. None of these host species are related to species of common ornamental roses, thus this rust species does not appear to be a threat to the North American and other rose industries.
All adult female Aulacaspis yasumatsui (cycad aulacaspis scale (CAS)) have a waxy outer covering for the protection of themselves and their eggs (the scale) (Weissling et al. 1999). The scale of mature females of A. yasumatsui are: "white, 1.2-1.6mm long and highly variable in form. They tend to have a pyriform shape with the exuviae at one end, but are often irregularly circular, conforming with leaf veins, adjacent scales and other objects. The ventral scale is extremely thin to incomplete. The scale of the juvenile male is similar to those of other species of Diaspididae, being 0.5-0.6mm long, white and tricarinate, with exuviae at the cephalic end. Scales of males are nearly always more numerous than those of females" (Howard et al. 1999). Adult males are orange-brown, and are similar in appearance to tiny flying midges, with one pair of wings and well-developed legs and antennae (Heu et al. 2003). Adult females are also orange in colour (Weissling et al. 1999).
Aulacaspis yasumatsui (cycad aulacaspis scale (CAS)) or the Asian cycad scale, is highly damaging to cycads, which include horticulturally important and endangered plant species. The cycad scale is an unusually difficult scale insect to control, forming dense populations and spreading rapidly, with few natural enemies in most localities where it has been introduced. The scale has the potential to spread to new areas via plant movement in the horticulture trade.
Aulacaspis yasumatsui (cycad aulacaspis scale (CAS)) is found on plants from the gymnosperm order Cycadales, which consists of three families - Cycadaceae (Cycas a genus that contains its preferred host species), Stangeriaceae (Stangeria) and Zamiaceae (8 genera). CAS has been recorded on plants of the following genera: Cycas, Stangeria, Dioon, Encephalartos, Ceratozamia, Macrozamia and Microcycas (Howard et al. 1999;J. Haynes, pers. comm.;W. Tang, pers. comm.). These plants represent a wide variety of geographic origin. At Montgomery Botanical Center in Miami, Florida, the heaviest infestations appeared to be on Cycas and Stangeria eriopus. The threatened king sago (see Cycas revoluta in IUCN Red List of Threatened Species) appears to be more susceptible to CAS than most other species (Heu et al. 2003). The cycad scale infests pinnae, rachides, strobili, stems and roots of these various species of cycads. It is primarily found on the underside of leaves (Howard et al. 1999). In containerised plants, CAS usually aggregates on primary roots (about 10mm in diameter), and singly or in groups of a few on secondary roots (about 2mm in diameter) near the container sides. In the field, CAS has been observed at different depths on primary (3cm in diameter) and secondary roots in groups of a few to several individuals from near the soil surface to a maximum depth of 60cm (Weissling et al. 1999).
The preferred host genus of CAS is Cycas, which is native to Asia, as is A. yasumatsui. This suggests that Cycas may be the original host (Howard et al. 1999). CAS has been identified mainly in the monsoon areas of southeast Asia, and has seldom been found on cycads in rainforest areas. This suggests that the ability of CAS to infest roots may be an adaptation to surviving brush fires, a common occurrence in these monsoon areas (Howard et al. 1999).
In South Africa, CAS has been recently reported from non-native and native cultivated cycad species (Nesamari et al., 2015).
Host Plants and Other Plants Affected
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Cycas revoluta (sago cycas)|Cycadaceae
List of Symptoms/Signs
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Growing point / dieback
Leaves / abnormal colours
Leaves / external feeding
Leaves / yellowed or dead
Roots / external feeding
Seeds / external feeding
Stems / external feeding
Biology and Ecology
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Female Aulacaspis yasumatsui (cycad aulacaspis scale (CAS)) can begin laying eggs within 21-35 days of hatching in warmer weather (Hamon, 2000;in IFAS, 2005). Eggs hatch within 8-12 days and some individuals have been observed to develop to second instars within 16 days, and third instars in 28 days. Mature females lay 100 eggs (Howard et al. 1999).
Generally, scale insects initially hatch into a “crawler” stage capable of movement. When they find a suitable spot on a plant, they will insert their stylet (straw-like mouthparts) into the plant and begin feeding. Shortly after this, they will begin to create a covering over themselves, and they stay this way until they die. (IFAS, 2005).
Male cycad scales emerge from their scale shortly before death and fly in search of females for mating before they die. Females remain attached to the plant until their death. (Haynes and Marler, 2005). Most female cycad scales do not live longer than 75 days (Howard et al. 1999).
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Natural enemy|Type|Life stages|Specificity|References|Biological control in|Biological control on
Cybocephalus nipponicus| Predator
Means of Movement and Dispersal
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Introduction pathways to new locations
Host: Aulacaspis yasumatsui (cycad aulacaspis scale (CAS)) can be transported to new locations by the import of infested cycad plants. There is high potential for CAS to spread in this manner as one or more fecund females hidden in the cycad can easily escape detection (EPPO, 2005).
Nursery trade: Aulacaspis yasumatsui (cycad aulacaspis scale (CAS)) can be transported to new locations by the import of infested cycad plants. There is high potential for CAS to spread in this manner as one or more fecund females hidden in the cycad can easily escape detection (EPPO, 2005).
Local dispersal methods
Garden escape/garden waste: The crawler stage of Aulacaspis yasumatsui (cycad aulacaspis scale (CAS)) can be spread via garden waste or infected pruning equipment (Hodges et al. 2003).
On animals: Aulacaspis yasumatsui (cycad aulacaspis scale (CAS)) can spread by "hitchhiking" on people,animals, birds, large insects etc. when in the crawler stage (Heu et al. 2003).
On animals (local): Aulacaspis yasumatsui (cycad aulacaspis scale (CAS)) can be carried by the wind when in the crawler stage (Heu et al. 2003) infesting plants more than a mile away (Moore, 2005).
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Nursery trade|| Yes
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Debris and waste associated with human activities|| Yes
Host and vector organisms|| Yes
Plants or parts of plants|| Yes
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Plant parts liable to carry the pest in trade/transport|Pest stages|Borne internally|Borne externally|Visibility of pest or symptoms
Pest or symptoms usually visible to the naked eye
Pest or symptoms usually visible to the naked eye
Stems (above ground)/Shoots/Trunks/Branches
Pest or symptoms usually visible to the naked eye
Plant parts not known to carry the pest in trade/transport
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General Impacts Compiled by IUCN SSC Invasive Species Specialist Group (ISSG) Aulacaspis yasumatsui (cycad aulacaspis scale (CAS)) threatens both ornamental and wild cycad populations. It spreads rapidly and can cover a large cycad within a number of weeks (Haynes & Marler, 2005). It has been observed to kill 100% of a Cycas revoluta population in cultivation within one year of infestation (Howard et al. 1999).
CAS has the potential to disrupt the horticultural trade in cycads. Cycads are valuable ornamental plants worldwide and the scale detracts from the appearance of plants even after treatment as the dead scales do not readily drop off (Howard et al. 1999). CAS also threatens the survival of several rare and already endangered species conserved in botanical collections (Howard et al. 1999;J. Haynes, pers. comm).
CAS can be easily spread to new locations via the plant trade as one or more fecund females on the plant can easily evade detection. This could threaten native cycad populations in these new locations (Emshousen et al. 2004), as is occurring in Guam where CAS is killing off the native cycad (see Cycas micronesica in IUCN Red List of Threatened Species) at an alarming rate (Haynes & Marler, 2005). It is expected that CAS will spread to other islands in the Caribbean and Micronesia unless strict controls are put in place to restrict its spread via commercial cycads.
Indigenous cycads in the genus Cycas in Micronesia would be at risk should the spread of CAS be left unchecked in these regions (Muniappan, 2005;J. Haynes, pers. Comm). CAS has been reported in the Taitung Cycad Nature Reserve, Taiwan, home of the endemic prince sago (see Cycas taitungensis in IUCN Red List of Threatened Species). A recent survey conducted in the reserve by the Taiwan Forestry Research Institute found that 90% of prince sago were infected by CAS, mortality was, however, found to be less than 3%.
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Threatened Species|Conservation Status|Where Threatened|Mechanism|References|Notes
Cycas micronesica|EN (IUCN red list: Endangered)| Guam|Herbivory/grazing/browsing| ISSG,
Cycas revoluta (sago cycas)|LC (IUCN red list: Least concern)|Herbivory/grazing/browsing| ISSG,
Cycas taitungensis|EN (IUCN red list: Endangered)| Taiwan|Herbivory/grazing/browsing| ISSG,
Risk and Impact Factors
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Invasive in its native range
Proved invasive outside its native range
Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
Has high reproductive potential
Negatively impacts forestry
Threat to/ loss of endangered species
Threat to/ loss of native species
Negatively impacts animal/plant collections
Likelihood of entry/control
Highly likely to be transported internationally accidentally
Difficult/costly to control
Similarities to Other Species/Conditions
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The scale of the female hibiscus snow scale (Pinnaspis strachani (Cooley)) resembles A. yasumatsui, but P. strachani is far less common on cycads in southern Florida (Howard et al. 1999).
In the field, female A. yasumatsui resemble the magnolia white scale (Pseudaulacaspis cockerelli (Comstock)), which is also common on cycads in Florida. The two can be distinguished under a 10X hand lens, with the scale removed, using three features: 1) the colour of the body of all stages and of the eggs of A. yasumatsui is orange, except recently molted individuals, which are yellow. The eggs and all stages of P. cockerelli are yellow. 2) A. yasumatsui has an expanded prosoma. 3) Scales of A. yasumatsui are usually more numerous on the lower surface of leaves, while those of P. cockerelli are more numerous on the upper surface (Howard et al. 1999).
Recent molecular analysis has shown that Acanthaster planci is in fact a species complex consisting of four distinct clades from the Red Sea, the Pacific, the Northern and the Southern Indian Ocean. Benzie (1999) had previously demonstrated the genetic differentiation between A. planci from the Pacific and the Indian Ocean, and this genetic grouping is reflected in the distribution of colour morphs: grey-green to red-brown in the Pacific Ocean, and blue to pale red in the Indian Ocean (Benzie, 1999). Colour combinations can vary from purplish-blue with red tipped spines to green with yellow-tipped spines (Moran, 1997). Those on the Great Barrier Reef are normally brown or reddish grey with red-tipped spines, while those in Thailand are a brilliant purple (Moran, 1997). Adult A. planci usually range in diameter from around 20 to 30cm (PERSGA/ GEF 2003) although specimens of up to 60cm (and even 80cm) in total diameter have been collected (Chesher, 1969;Moran, 1997). The juvenile starfish begins with 5 arms and develops into an adult with an astounding 16 to 20 arms, all heavily armed with poisonous spines 4 to 5cm in length, which can inflict painful wounds (Moran, 1997;Birk, 1979). Arm values vary between localities with a range of 14 to 18cm given for the Great Barrier Reef (Moran 1997). Starfish are usually concealed during daylight hours, hiding in crevices (Brikeland and Lucas, 1990;Chesher, 1969). Groups of starfish often move as huge masses of 20 to 200 individuals, presenting a terrifying "front" which destroys the reef as it moves through (Chesher, 1969). Signs of starfish presence are obvious;the coral skeleton is left behind as the result of starfish feeding and stands out sharply as patches of pure white, which eventually become overgrown with algae (Chesher, 1969). In some cases, herbivorous sea urchins move in to feed on algae, creating a pattern against the white coral that resembles the holes of swiss cheese (Tsuda et al. 1970).
Coral gardens from Micronesia and Polynesia provide valuable marine resources for local communities and environments for native marine species such as marine fish. In coral ecosystems already affected by coral bleaching, excess tourism and natural events such as storms and El Nino, the effects of the invasive crown-of-thorns starfish (Acanthaster planci) on native coral communities contributes to an already dire state of affairs. Acanthaster planci significantly threatens the viability of these fragile coral ecosystems, and damage to coral gardens by the starfish has been quite extensive in some reef systems. Outbreaks in the Pacific appear to be more massive and widespread than those elsewhere. This may reflect different patterns of outbreak between Pacific and Indian Ocean populations, which have recently been shown to form separate clades of an A. planci species complex. (Vogler et al. 2008;and see 'Description' section).
The yellow or pale-orange, elongate-oval eggs, are ca 1.2 mm long. They are laid in groups of 12-25 on the underside of potato leaves. The females glue them to the leaf by one end using a special secretion. The long axis of the egg is almost perpendicular to the leaf. Eggs within a mass tend to form irregular rows and hatch simultaneously.
Body strongly convex dorsally, with large abdomen. Head, bearing 6 ocelli behind the antenna on each side and a pair of 5-dentate mandibles. Three thoracic segments, each bearing a pair of 3-segmented legs, plus claw. Abdomen 9-segmented. Colour changing with development, first instar cherry-red with shiny, black head and legs;later instars becoming progressively carrot-red, then pale orange in final instar.
Head, legs and posterior part of pronotum black to deep brown;two conspicuous rows of dark spots occur on the lateral aspects of the mesothoracic and abdominal segments 1 to 7, the uppermost surrounding the spiracles, and also segments 8 and 9 with dark dorsal plates. Setae when present are very small, some occur on the head, legs, pronotum, on the pigmented areas and ventrally. Spiracles small, annular with black peritremes and situated on the mesothorax and first 8 abdominal segments. Body length of full-grown larva about 15 mm.
A detailed generic diagnosis of Leptinotarsa larvae is provided by Cox (1982) and the first instar is described by Peterson (1951). The weights of the four larval instars are given by Balachowsky (1963).
Yellowish, bearing short setae on low, conical, brown tubercles. Head bearing several short setae, mandibles apically unidentate. Thorax with pronotum bearing about 100 setae;meso- and metathorax much more sparsely setose;apices of femora bearing about 3-5 setae and apical tarsal segment 1 seta. Abdominal segments 1-6 with lateral expansion dorsal to spiracle, dorsally bearing about 48 short setae, laterally about 9 setae on large papilla ventral to spiracle. Apical abdominal segment bearing a single, brown, median, sharply-pointed urogomphus or spine. Spiracles situated on mesothorax and abdominal segments 1-8;peritremes dark brown, but pale on abdominal segments 6-8. For further details, see Cox (1996).
Head, pronotum and venter yellow-orange with black markings, legs and scutellum orange-yellow, elytra yellow-orange with five longitudinal black stripes. Apical segment of maxillary palpi cylindrical, rounded apically, shorter than preceding segment. Elytra punctate-striate, epipleura glabrous. Mesosternum not raised above level of prosternum. Profemora normal, third tarsal segment entire, tarsal claws simple, divergent, not fused basally. Body length 8.5-11.5 mm.
The genus was revised by Jacques (1988). A key to the North American species is given by Wilcox (1972) and Jacques (1985).
Adults and larvae are easily seen because of their large size. L. decemlineata has a tendency to release its hold on plants that are shaken and this characteristic can be used to detect insects hidden among foliage. Visual sampling of potato fields was as efficient for estimating population density as the whole-plant bag-sampling method, and more efficient than sweep netting (Senanayake and Holliday, 1988). Soil sampling at harvest for buried beetles in diapause provides reliable results in area surveys (Glez, 1983). A sequential sampling plan has been reported for estimating populations of Colorado potato beetle egg masses and of adults and larvae (Hamilton et al., 1997a).
Colorado beetle principally attacks an introduced field crop grown as a monoculture, but not to an extent that has affected the area of the crop grown. It is not accordingly invasive in the usual environmental sense. It has no effects on the environment.
L. decemlineata attacks potatoes and various other cultivated crops including tomatoes and aubergines. It also attacks wild solanaceous plants, which occur widely and can act as a reservoir for infestation. The adults feed on the tubers of host plants in addition to the leaves, stems and growing points.
The brown eggs are elliptical, about 1.5 mm long and 1 mm wide, with each end broadly rounded. The slightly convex upper surface has the chorion with a honeycomb sculpturation. They are fixed to the leaf surface by a cementing substance (Maulik, 1938).
The larvae are whitish in colour. The first-, second- and final-instar larvae are described in detail by Maulik (1938). The head of the first stage larva is comparatively large compared with the body. The entire cuticle is more densely covered with minute spicules. A seta arises from about the middle of the lateral margin of each thoracic segment, with two setae on each of the abdominal lateral processes. Each process of the tail-shovel bears a large, sharp, curved spine at the inner angle, and a series of five or six setae along the dorsal and ventral margins. The larva is about the same length as the egg, but about 0.75 mm in width.
The second-instar larva resembles the full-grown larva more than the first instar. The lateral abdominal processes are longer, each bearing four setae which are comparatively longer than those of the fully developed larva and situated at different points around the periphery of the apex. There are eight setae on the prothorax (four on each side) and six on the meso- and metathorax (three on each side, two setae on the produced part and one posteriorly). The distinct spine at the inner angle of each prong of the tail-shovel is not prominent as in the first-instar.
The fully developed larva has the body moderately flat, almost parallel-sided, very slightly and gradually narrowed from the prothorax towards the apex, composed of 13 segments (one head, three thoracic and nine abdominal). It is almost 9 mm long and 2.25 mm wide. The anus is situated ventrally on the ninth segment, if the fold at the anal orifice is considered as representing a segment, then the abdomen should be regarded as 10-segmented. The distinct head bears a pair of 2-segmented antennae;a group of five ocelli, three in a line and two in another, situated behind the antennae;a pair of apically bidentate mandibles.
The thoracic segments are broader than they are long, the mesothorax very slightly broader than the prothorax and the metathorax very slightly broader than the mesothorax. The dorsal surface of the prothorax is more strongly sclerotized with a fine median suture and laterally rounded. The meso- and metathorax bears laterally a small knob in the middle, bearing two fine, short setae. There is a pair of well developed 3-segmented legs on each thoracic segment, each terminating in a single claw and fleshy pad-like structure. Each of the first seven abdominal segments is broader than it is long;each of the first three segments is somewhat shorter than the following segments;the eighth and ninth together form the terminal tail-shovel. Each segment bears laterally a moderately long process, ventral to the spiracles. A lateral process is a conical structure projecting horizontally nearly from the middle of the margin, except in the fifth, sixth and seventh segments, in which they appear to arise more from the posterior part. The apical part is subconical and distinctly thinner than the basal part. The entire surface is densely covered with spinules. The apical part bearing three or four setae. The tail-shovel is longer than broad, apically deeply concave, the prongs bent inwards and bluntly-pointed. The upper ridge on each side bearing nine spinules, three smaller on the basal part nearer the large spiracle, four larger on the middle part and two smaller on the bent apical part. There are 4 small spinules on the lower ridge more widely spaced than those on the upper ridge. The upper surface is concave, bearing many irregularly placed transparent areas and the ventral surface is flat. There are 9 pairs of spiracles, one thoracic, between the pro- and mesothorax, situated on a conical structure resembling a lateral process, and one pair dorsally situated on each of the first seven abdominal segments.
The larvae undergo five instars which can be distinguished on the morphometrics (in mm) of the tail-shovel as follows: L1, 0.33, mean 0.13;L2, 0.47, mean 0.20;L3, 0.65, mean 0.29;L4, 0.82, mean 0.37;L5, 0.94, mean 0.45.
Dorsal habitus views of the first-, second- and final-instar larvae are provided by Maulik (1938).
Generic and specific keys to separate the larvae of Brontispa species are provided by Gressitt (1963). The key characters are: body not oval with a continuous margin;head visible from above;last abdominal segment with a caudal process;not leaf-mining;meso- and metathoracic segments lacking lateral processes;caudal process with arms widely separated basally, thickened or strongly angulate posteriorly;lateral abdominal processes short and blunt, rarely last two longer;spiracle of last segment elliptical (Generic);lateral abdominal processes subequal, eighth shorter than greatest width of an arm of caudal process;emargination of caudal process usually broader than long;arms of caudal process parallel-sided externally, at least in central part;emargination of caudal process reaching about half way from apices of arms to spiracles;emargination of caudal process not much broader than long, broadly oval, widest in middle;arm curved and subacute apically;eighth abdominal process shorter than preceding (Specific).
The pupae of several Brontispa spp. including B. longissima are described by Maulik (1938). The head bears three processes, one median and one on each side. Each lateral process is fleshy, broadest basally, pointed apically, pre-apically bearing small blunt spine. Thorax with meso- and metanotum each bearing a pair of wings. The abdomen is 9-segmented, the eighth and ninth segments are fused. Each of the first six segments bears laterally a pair of spiracles opening dorsally. Each segment bearing spinules arranged as follows: no spinules on first segment;from segments 2 to 7, two groups of four in transverse line, one nearer the basal margin and the other nearer the apical, those of the basal group are comparatively larger and more widely-spaced, those of the apical line are situated in the intervals of the spinules of the basal group;on segment 8 only two in transverse line near the basal margin. Dorso-laterally bearing a longitudinal series of spinules, one on each of the first seven segments, situated a little posterior to and more inward than the corresponding spiracle (on the seventh in a similar position). Anterior to each spiracle on segments 3 to 6 and in a similar position on 7 is a spine. Laterally on segments 1-7 bearing a group of closely placed spinules bearing moderately long setae, the spinules being less prominent on segments 1-2, or 3. Ventrally, only segments 4-7 bearing spinules. The prongs of the tail-shovel are more slender, somewhat longer than those of the larva, and also lack lateral spines or setae. The last larval exuvium is always retained on the prongs of the tail-shovel.
The adults 8.5-9.5 mm long, 2.00-2.25 mm wide;length of antenna, 2.75 mm. The males are slightly smaller than females (Maulik, 1938). Their colour varies geographically from reddish-brown in Java, to almost black in the Solomon Islands and Irian Jaya. Some specimens have the elytra brown or black, or have a spindle-shaped black marking on the elytral suture. Considerable overlapping of these forms, which were long regarded as distinct species, occurs (Lever, 1969). Maulik (1938) examined the male genitalia, especially the median lobes of the different colour varieties, and found no differences. However, the median lobes of distinct species, for example B. linearis and B. longissima, exhibit obvious structural differences.
Maulik (1938) and Gressitt (1963) have provided keys to separate the adults of Brontispa species. The relevant key characters for B. longissima are: antennae not serrate;central portion of head usually parallel-sided, broader than long;rostrum more than half as long as first antennal segment;pronotum flattish, shiny, with several large impunctate areas;body quite flat and narrow;prothorax laterally distinctly concave;anterior lateral angles of pronotum expanded, expanded portion broadly-rounded, constricted behind, without a minute projection at inner angle.
The host range of B. longissima includes various Palmae [Arecaceae]. In Papua New Guinea, coconut, sago palms, areca or betel palm (Areca catechu), royal palms (Roystonea regia), oil palm and ornamental palms are attacked. In northern Australia, hosts include areca palms (A. catechu), nicobar palm (Bentinckia nicobarica), carpentaria palm (Carpentaria acuminata) and fish tail palm (Caryota mitis). In Hong Kong, it is also reported from ivory nut palm (Phytelephas), petticoat palm (Washingtonia robusta), king palm (Archontophoenix alexandrae) and dwarf date palm (Phoenix roebelenii) (CSK Lau, Agriculture and Fisheries Department, Hong Kong, personal communication, 1992).
S. podophyllum is a vine attaining up to 10 metres in length, climbing by means of adventitious roots produced at the nodes. Stems cylindrical, glaucous, 1-2 cm in diameter, producing milky latex when wounded. Juvenile plants with hastate leaves;adult plants with dimorphic leaves, the basal leaves hastate, the distal leaves digitate, with 3-11 leaflets, coriaceous, united or free at the base, the basal leaflets smaller and auriculate at the base, the middle leaflets 16-38 ? 6-17 cm, obovate, elliptical, or lanceolate, with acuminate apex;petioles 15-60 cm long, almost cylindrical;inflorescences in groups of 4-11, ascendant;peduncles 8-9 cm long, slender;spathe ca. 10 cm long, convolute at the base to form a tube, the limb cream-coloured on the inner surface, green outside, concave, ephemeral;spadix whitish, sessile, cylindrical, with a constriction between the area of pistillate flowers and the staminate flowers. Fruit is a syncarp, ovoid, red, reddish orange, or yellow, 3-5.5 cm long (Acevedo-Rodr’guez, 2005;Acevedo-Rodr’guez and Strong, 2005).
Dovyalis caffra is a dioecious shrub or small, evergreen tree, usually 3-5 m in height with a many-branched crown. The smooth bark is grey on young branches, though fissured and flaky to corky on old branches and stems. Young branches are heavily armed with long (4-7 cm) spines, but the stem has few spines. The simple leaves occur in tight clusters on dwarf lateral branches and alternate on young shoots. Each leaf is obovate 2-5.5 cm by 0.5-3 cm with a rounded apex and tapering base on 5 mm-long petioles. The small creamish-green flowers occur in dense clusters. The male flowers are 3 mm long in dense clusters of five to 10, while the female flowers are solitary or occur in groups of up to three on stalks 4-10 mm long in the leaf axils. The fleshy fruit is almost spherical and up to 6 cm in diameter. The fruit skin turns from green to yellow-orange with a velvety surface when ripe. The pulp encloses about 12 hairy seeds in two circles.
P. macarthurii is a palm tree. Stems grow in dense clumps or rarely solitary, up to 9 m tall, only 7 cm in diameter, thus appearing bamboo-like. Leaves are up to 3 m or more long, compound. Leaflets are 15-40 on each side, more or less regularly arranged, with margins nearly parallel or tapered at the tip. Inflorescences are up to 20-45 cm long, bearing flowers in groups of three consisting of two male and one female flower. Male flowers with sepals 3, approximately 1.5-2.5 mm long, yellow-green to light green;petals 3, approximately 7 mm long, yellow-green to light green;stamens 23-40 per flower;ovary, style and stigma well developed but the ovules are absent in the male flowers. Female flowers with sepals 3, 2 x 3 mm, cream-green;petals 3, 3-4 x 2-3.5 mm, cream-green;3-6 staminodes present;stigma 0.5 mm long, recurved. Fruits ovoid, 12-16 mm long, red when mature. Seed 9-12 mm long, 5-angled.
Evidence for a Viral Agent
A virus, BBTV, is the causal agent of bunchy top disease of banana. Although unequivocal evidence by reproduction of the disease through inoculation of purified virions or cloned genomic components is lacking, definitive association of BBTV with bunchy top disease was demonstrated by insect vector-mediated transmission of BBTV from an infected banana to a healthy banana plant. The virions are intimately associated with the disease (Harding et al., 1991;Thomas and Dietzgen, 1991) and have been detected in all symptomatic plants tested (Dietzgen and Thomas, 1991;Thomas, 1991;Thomas and Dietzgen, 1991;Karan et al., 1994;Kumar et al., 2011). Dale et al. (1986) and an published study (ML Iskra-Caruana, Montpellier, France) isolated dsRNA, suggestive of luteovirus infection, from Cavendish cultivars and from bunchy top affected plant samples. However, neither these, nor any subsequent studies, have identified or established a role for any virus other than BBTV in banana bunchy top disease aetiology.
Particle and Genome Properties
The virions of BBTV are icosahedra, ca 18-20 nm in diameter, have a coat protein of ca 20,000 Mr, a sedimentation coefficient of ca 46S and a buoyant density of 1.29-1.30 g/cm³ in caesium sulphate (Wu and Su, 1990c;Dietzgen and Thomas, 1991;Harding et al., 1991;Thomas and Dietzgen, 1991). Purified preparations have an A 260/280 of 1.33 (Thomas and Dietzgen, 1991). The virus possesses a multi-component genome, consisting of at least six circular, single-stranded DNA (ssDNA) components each ca. 1000-1100 nucleotides long, previously referred to as DNA-1 to -6 (Wu et al., 1994;Yeh et al., 1994;Burns et al., 1995;Xie and Hu, 1995). However, they were renamed as DNA-R, -U3, -S, -M, -C and -N. The DNA-R component encodes two open reading frames and other components each encode one protein (Burns et al., 1995;Dale et al., 1986;Beetham et al., 1997). Two areas of the non-coding regions are highly conserved between the six components (Burns et al., 1995). The first is a stem-loop common region of up to 69 nucleotides. It contains a nonanucleotide loop sequence conserved amongst ssDNA plant viruses and which may be involved in rolling circle replication and initiation of viral strand DNA synthesis. The second, 5' to the stem-loop common region, is a major common region varying in size between components from 65 to 92 nucleotides and which may have a promoter function. The initiation factor for endogenous DNA primers is also located within the major common region (Hafner et al., 1997a). DNA-R (c omponent 1) encodes a putative replication initiation protein and contains a second functional open reading frame internal to this, referred as U5, the function of which is unknown;whilst DNA-S (component 3) codes for the coat protein (Harding et al., 1993;Dale et al., 1986;Hafner et al., 1997b, Wanitchakorn et al., 1997). DNA-U3 (component 2) codes a protein of unknown function, DNA-M (component 4) codes for movement protein, DNA-C (component 5) has been shown to produce a gene product containing an LXCXE motif and to have retinoblastoma protein (Rb)-binding activity, known to perform cell-cycle-link protein, and DNA-N (component 6) codes for a nuclear shuttle protein. The gene product may be produced very early in the infection cycle and be responsible for switching the first infected cells to S-phase in preparation for virus replication. Recent research indicates that component 1 is the minimal replicative unit of BBTV and encodes the 'master' viral Rep (Horser et al., 2001a). Additional Rep encoding circular ssDNA components were reported in a few BBTV isolates from East Asia and the South Pacific region (Horser et al., 2001b). They were named BBTV-S1 and BBTV-S2, of 1109 and 1095 nts, and encoded a protein similar to the DNA-R segment but the genomic organization differed from that of DNA-R. The –S1 and –S2 components lack internal ORF U5, and the stem loop sequence was not similar to the six genomic components. These sequences were not considered as an integral part of the BBTV genome but the precise function of these additional DNAs was not known.
Strains of BBTV
Most isolates of BBTV are associated with typical severe disease symptoms. However, mild and symptomless isolates have been reported from Taiwan (Su et al., 1993;Djailo et al., 2016). BBTV has been confirmed in specimens of mild and symptomless infections from Taiwan by both ELISA and PCR (HJ Su, JL Dale and JE Thomas, Brisbane, personal communication, 1996) and the isolates can be transmitted by Pentalonia nigronervosa (HJ Su, Taipei, personal communication, 1996). Genomic differences, which correlate with these biological variants, have not yet been determined.
Two broad groups of isolates have been identified on the basis of nucleotide sequence differences between some, possibly all, of the six recognized genome components (Karan et al., 1994;Hu et al., 2007;Kumar et al., 2015;Qazi, 2016). The 'South Pacific' group (also referred as Pacific Indian Ocean (PIO) group) comprises isolates from Australia, Bangladesh, India, Myanmar, Pakistan, Sri Lanka, Fiji, Western Samoa, Tonga, Hawaii (USA) and all the isolates identified, as of 2017, in Africa (Angola, Benin, Burundi, Cameroon, CAR, Congo, DRC, Egypt, Equatorial Guinea, Gabon, Malawi, Nigeria, Rwanda, South Africa and Zambia), whilst the 'Asian' group (also referred as Southeast Asian (SEA) group) comprises isolates from China, Indonesia, Japan, the Philippines, Taiwan, Thailand and Vietnam. These differences are present throughout the genomes of components 1 and 6, but are most striking in the untranslated major common region. No biological differences have been associated with these sequence differences.
Magee (1948) noted that certain plants of 'Veimama', a cultivar originally from Fiji and growing then in New South Wales, showed a 'partial recovery' from bunchy top symptoms and produced bunches. After an initial flush of typical severe symptoms in three or four leaves, subsequent leaves showed few, if any, dark-green flecks. Suckers derived from these partially recovered plants also displayed a flush of typical symptoms followed by partial recovery. The origin of the infection, whether from Australia or Fiji, was uncertain. This partial recovery was noted for some infected plants of 'Veimama' only, and in Fiji was noted for one sucker only on a single infected stool from among hundreds of infected stools of 'Veimama' observed. Magee was not able to transmit the virus from partially recovered plants and was only able to super-infect them, with difficulty, with high inoculum pressure. This may be an example of a mild strain of BBTV, possibly a non-aphid transmitted one, propagated vegetatively, reaching only a low titre and conferring a degree of cross-protection. Alternatively, 'Veimama' may not be uniform and individual plants with a degree of resistance may exist. The complete explanation for this phenomenon is unclear. Evidence from recent studies suggests the occurrence of Musa cultivars with variable response to BBTV infection, ranging from extreme to moderate susceptibility and recovery associated with reduced virus titre (Ngatat et al., 2017;PL Kumar, IITA, Nigeria, personal communication, 2017). It is likely that previous observations of mild symptoms and lack of aphid-transmission may be related to virus-host interaction rather than to mild strains.
The inability to transmit bunchy top from abacá to banana (Ocfemia and Buhay, 1934) was originally considered evidence that two distinct strains of the virus existed. However, recent studies have identified a new virus, Abaca bunchy top virus (ABTV) which also belongs to the genus Babuvirus, as the cause of bunchy top-like symptoms in abacá (Sharman et al., 2008). The possibility of co-infection or single infection of BBTV and ABTV in abacá cannot be ruled out in endemic regions.
The typical symptoms of bunchy top of banana are very distinctive and readily distinguished from those caused by other viruses of banana. Plants can become infected at any stage of growth and there are some initial differences between the symptoms produced in aphid-infected plants and those grown from infected planting material.
In aphid-inoculated plants, symptoms usually appear in the second leaf to emerge after inoculation and consist of a few dark-green streaks or dots on the minor veins on the lower portion of the lamina. The streaks form 'hooks' as they enter the midrib and are best seen from the underside of the leaf in transmitted light. The 'dot-dash' symptoms can sometimes also be seen on the petiole. The following leaf may display whitish streaks along the secondary veins when it is still rolled. These streaks become dark green as the leaf unfurls. Successive leaves become smaller, both in length and in width of the lamina, and often have chlorotic, upturned margins. The leaves become dry and brittle and stand more erect than normal giving the plant a rosetted and 'bunchy top' appearance.
Suckers from an infected stool can show severe symptoms in the first leaf to emerge. The leaves are rosetted and small with very chlorotic margins that tend to turn necrotic. Dark-green streaks are usually evident in the leaves.
Infected plants rarely produce a fruit bunch after infection and do not fruit in subsequent years. Plants infected late in the growing cycle may fruit once, but the bunch stalk and the fruit will be small and distorted. On plants infected very late, the only symptoms present may be a few dark green streaks on the tips of the flower bracts (Thomas et al., 1994).
Mild strains of BBTV, which induce only limited vein clearing and dark-green flecks, and symptomless strains have been reported in Cavendish plants from Taiwan (Su et al., 1993). Mild disease symptoms are expressed in some banana cultivars and Musa species. The dark-green leaf and petiole streaks, so diagnostic and characteristic of infection of cultivars in the Cavendish subgroup, can be rare or absent (Magee, 1953). Some plants of 'Veimama' (AAA, Cavendish subgroup), after initial severe symptoms, have been observed to recover and to display few if any symptoms.
BBTV is the most serious virus disease of bananas and plantains. It occurs in Africa, Asia, Australia and South Pacific islands. The virus is transmitted in a persistent, circulative, non-propagative manner by the banana aphid, Pentalonia nigronervosa, which has worldwide distribution. The virus is also spread through infected planting material. All banana cultivars are thought to be susceptible, with no known sources of resistance.
In the Musaceae, BBTV is known to infect a range of Musa species, cultivars in the Eumusa (derived mainly from M. acuminata and M. acuminata x M. balbisiana) and Australimusa (derived mainly from M. maclayi, M. lolodensis and M. peekelii) series of edible banana and Ensete ventricosum (enset). Susceptible Musa species include M. balbisiana (Magee, 1948;Espino et al., 1993), M. acuminata ssp. banksii, M. textilis (abacá) (Magee, 1927), M. velutina (Thomas and Dietzgen, 1991), M. uranoscopos, M. jackeyi, M. ornata and M. acuminata ssp. zebrina (ADW Geering and JE Thomas, Brisbane, personal communication, 1998).
To date, there are no confirmed reports of immunity to BBTV in any Musa species or cultivar. However, differences in susceptibility between cultivars subject to either experimental or field infection have frequently been noted (Magee, 1948;Muharam, 1984;Espino et al., 1993;Ngatat et al., 2017).
Espino et al. (1993) evaluated a total of 57 banana cultivars for their reaction to bunchy top, both by experimental inoculation and field observations. All cultivars in the AA and AAA genomic groups were highly susceptible. However, low levels of infection (as assessed by symptom expression) or total absence of symptoms following aphid inoculation was noted in some cultivars containing the B genome. These included 'Radja' (AAB, syn. 'Pisang Raja' - 12.5% of inoculated plants with symptoms), 'Bungaoisan' (AAB, Plantain subgroup - 0%), 'Pelipia' (ABB, syn. Pelipita' - 10%), 'Pundol' (ABB - 0%), 'Katali' (ABB, syn. 'Pisang Awak' - 0%), 'Abuhon' (ABB - 0%) and 'Turangkog' (ABB - 0%).
These cultivars were not back-indexed by aphid transmission to a susceptible banana cultivar or tested biochemically (for example, by ELISA), so the presence of symptomless infection cannot be ruled out. Also, greater numbers of aphids than the 15 used here may have resulted in infection. Cultivars 'Abuhon' and 'Bungaoisan' are susceptible to BBTV by experimental aphid inoculation (ADW Geering and JE Thomas, Brisbane, personal communication, 1998). Nevertheless, it appears that real differences exist in cultivar reaction to bunchy top and the time taken before symptoms are expressed.
Evaluation of 16 Musa genotypes in Cameroon comprising plantain landraces, Cavendish bananas and synthetic hybrids revealed a high level of tolerance to BBTV in Gros Michel (AAA, Cavendish sub-group) and Fougamou (ABB cooking banana) (Ngatat et al., 2017). In another study of 40 Musa genotypes in Burundi, 8 genotypes (Musa balbisiana type Tani (BB), Kayinja (ABB), FHIA-03 (AABB), Prata (AAB), Gisandugu (ABB), Pisang Awak (ABB), Saba (ABB) and Highgate (AAA, Gros Michel subgroup)) were found to be asymptomatic, although Pisang Awak, Saba and Highgate tested positive to virus indicating tolerance to BBTV in some genotpyes (Niyongere et al., 2011).
Cultivars within the Cavendish subgroup form the basis of the international banana export trade and are generally highly susceptible to bunchy top. However, it appears that not all cultivars with an AAA genome are similarly susceptible. 'Gros Michel' exhibits resistance to the disease under both experimental inoculation and field conditions and Magee (1948) considered that the introduction of this cultivar to Fiji in the early 1900s contributed to partial rehabilitation of the bunchy top-devastated industry. Compared to 'Williams' (AAA, Cavendish subgroup), the concentration of virions of BBTV in infected plants of 'Gros Michel' and the proportion of plants infected by aphid inoculation is lower. Symptoms are also slower to develop and are less severe (Ngatat et al., 2017;ADW Geering and JE Thomas, Brisbane, Australia, unpublished, 1997). These factors may contribute to a reduced rate of aphid transmission and field spread in plantations of 'Gros Michel' (Ngatat et al., 2017).
There is no evidence for hosts outside the Musaceae, though reports have been conflicting. Su et al. (1993) obtained positive ELISA reactions from BBTV-inoculated Canna indica and Hedychium coronarium, and recovery of the virus to banana, though not reported here, was demonstrated (HJ Su, Taipei, personal communication, 1996). Ram and Summanwar (1984) reported Colocasia esculenta as a host of BBTV. However, Hu et al. (1996) were unable to demonstrate C. esculenta or Alpinia purpurata as experimental (E) or natural (N) hosts of BBTV in Hawaii. Geering and Thomas (1996) also found no evidence for the following species as hosts of BBTV in Australia: Strelitzia sp. (N), C. indica (E, N), C. x generalis (N), C. x orchiodes (N), H. coronarium (E), Helocania psittacorum (E), Alpinia coerulea (E, N), A. arundinelliana (E), A. zerumbet (E), Alocasia brisbaensis (E, N) or C. esculenta (E, N). Magee (1927) was unable to infect Strelitzia sp., Ravenala sp., Canna sp. (including C. edulis), Solanum tuberosum and Zea mays. Since the advent of improved and reliable diagnostics for BBTV, searches for alternative hosts outside the Musaceae, including those earlier suspects, have turned out to be negative.
Primary hosts are banana cultivars derived from M. acuminata and M. acuminata x M. balbisiana, and Musa textilis (abacá).
Aecia amphigenous, generally hypophyllous, scattered or grouped, rounded, minute, 0.3-0.5 mm diameter, elongated on veins, up to 5 mm long, yellow, surrounded by numerous hyaline, cylindrical paraphyses, rounded at apex, 50-75 x 5-8 µm;aeciospores globoid to ellipsoid, sparsely aculeate, yellow, 18-28 x 16-22 µm, wall 2-3 µm thick, with 3-7 pores. Uredinia hypophyllous, scattered, obicular, 0.5-2.0 mm diameter, pulverulent, orange;urediniospores subglobose or obovate, 18-28 x 15-20 µm, echinulate;wall 1-2 µm thick, 5-6 pores, scattered. Telia hypophyllous, scattered or in groups, 1-3 mm diameter, pulvinate, black;teliospores cylindric or fusiform, 3-6-septate, 52-110 x 25-32 µm;wall 3-4 µm, densely verrucose, chestnut-brown, each cell with 3-4 pores;pedicels persistent, hyaline, up to 160 µm long, wider at the base. See Cooke (1871), Cunningham (1931) and Wilson and Henderson (1966) for more detailed descriptions.
There is little published information on this plant pathogenic fungus, which is limited to parts of Asia, Europe and New Zealand. It attacks Rubus spp., among others, and as these hosts exist in other regions of the world with similar environmental conditions, this species may pose a threat to native or agricultural plants if introduced.
Uredinia hypophyllous, scattered or in small groups, circular, minute, 0.2-0.8 mm diameter, early exposed, somewhat pulverulent, orange-yellow;paraphyses numerous, cylindrical or clavate, 50-80 × 12-20 µm, somewhat incurved, walls thin (1 µm), smooth, colourless;urediniospores globose, subglobose, obovate or broadly ellipsoid, 18-28 × 14-22 µm minutely echinulate, colourless;wall 1.5 µm thick;contents orange-yellow. Telia hypophyllous, scattered or aggregate, minute, round or irregular, 0.2-0.4 mm diameter, early exposed, pulverulent, black;teliospores cylindrical, 4-6-septate, 59-98 × 27-35 µm, without apical papilla, rounded at both ends, not or slightly constricted at each septum;wall smooth (verrucose in Wei, 1988), 2.5-4.0 µm thick, sometimes slightly thickened above up to 5 µm, with three germ pores in each cell;pedicels colourless, persistent, up to 103 µm long, hygroscopic. See Wei (1988) for a more detailed description.
There is little published information on this plant pathogenic fungus, which is limited to Shaanxi, China and Taiwan. It infects Rubus spp., which exist in other regions of the world with similar environmental conditions, therefore this species may pose a threat to native or agricultural plants if introduced.
Uredinia hypophyllous, scattered or in small groups, minute, circular, yellow, pulverulent, 0.4 mm diameter;paraphyses clavate, erect or incurved, hyaline;urediniospores globose, broadly ellipsoid to obovoid, 17-23 x 14-20 µm;walls 1.0-1.5 µm thick, coarsely echinulate, pale-yellow. Telia hypophyllous, scattered or gregarious, minute, round, 0.7-2.5 mm diameter, pulverulent, black;teliospores cylindrical, (2-)5(-8)-septate, 40-116 x 25-42 µm, rounded at apex, more or less constricted at septum;walls 2.5-5.0 µm thick, orange-brown to blackish-brown, somewhat verrucose, two to three germ pores in each cell;pedicels hyaline, persistent, 100-144 µm long. See Wei (1988) for a more detailed description.
There is little published information on this plant pathogenic fungus, which has limited geographic distribution. It infects Rubus spp., which exist in other regions of the world with similar environmental conditions, therefore this species may pose a threat to native or agricultural plants if introduced.
Uredinia hypophyllous, scattered or irregularly grouped, round or sub-round, 0.3-0.8 mm diameter, early naked, pulvinate, finally pulverulent, orange-yellow, pale-yellow;paraphyses clavate, 34-70 x 7-16 µm, erect or incurved, wall smooth, colourless, uniformly thin, 1 µm;urediniospores subglobose, obovate, pyriform, ellipsoid or irregularly ellipsoid, 18-30 x 13-21 µm;walls 1.5 µm thick, densely and coarsely echinulate, inconspicuous or smooth at the base;contents orange-yellow or pale-yellow. Telia hypophyllous, scattered or gregarious, round or ellipsoid, 0.2-0.7 mm diameter, subpulvinate, early naked, reddish-brown;teliospores cylindrical, (1-)2-3(-5)-septate, 38-106 x 18-28 µm, rounded at the apex, rounded or somewhat attenuate at the base, not or slightly constricted at the septum, two or three germ pores in each cell, walls 2-3 µm, pale yellow-brown, with three to five rows of warts, pedicels sub-hyaline, persistent, 20-114 x 10-16 µm, 1-septate, not hygroscopic. See Wei (1988) and Hiratsuka et al. (1992) for more detailed descriptions.
There is little published information on this plant pathogenic fungus, which is limited to parts of Asia. It infects Rubus spp., which exist in other regions of the world with similar environmental conditions, therefore this species may pose a threat to native or agricultural plants if introduced.
Uredinia hypophyllous, scattered or in small groups, minute, irregularly round, early naked, pale-yellow, pulverulent;paraphyses clavate, 35-50 x 8-12 µm, suberect or incurved, wall hyaline;urediniospores subglobose, obovate or broadly ellipsoidal, 18.0-25.5 x 10.0-16.5 µm;walls 1.0-1.5 µm thick, minutely echinulate, hyaline. Telia hypophyllous, scattered or gregarious, minute, round or irregular in shape, pulverulent, black;teliospores oblong-cylindrical, 2-3-septate, 40-60 x 21-27 µm, rounded at apex, not constricted at septum, walls 4-6 µm thick, olive-brown, minutely and closely verrucose, without apical papilla, with three germ pores in each cell, pedicels hyaline, persistent, up to 60 µm long, hyaline. See Hiratsuka et al. (1992) for a more detailed description.
Uredinia hypophyllous, scattered or in small groups, minute, round, orange-yellow, pulverulent 0.1-0.6 mm;paraphyses clavate, erect or incurved, wall uniformly thin, 1 µm, hyaline;urediniospores globose to subglobose, obovate, broadly ellipsoid or obovoid, 18-26 x 16-23 µm, walls 0.8-1.5 µm thick, densely and coarsely echinulate, hyaline, contents orange-yellow or pale-yellow, germ pores obscure, approximately four to five, scattered. Telia hypophyllous, scattered or gregarious, minute, round or irregular, 0.2-0.6 mm diameter, pulverulent, black;teliospores cylindrical, (3-)6-7(-9)-septate, 63-147 x 24-43 µm, rounded at apex, not constricted at the septa, walls 4-6 µm thick, chocolate-brown, minutely and closely verrucose, with three germ pores in each cell, apical papilla lacking;pedicels hyaline, persistent, 53-119 µm long.
There is little published information on this plant pathogenic fungus, which has a limited geographic distribution. As hosts exist in other regions of the world with similar environmental conditions, this species may pose a threat to native or agricultural plants if introduced.
Aecia hypophyllous, mostly on veins or on petioles, peduncles and buds, rounded or irregular in shape, confluent, soon naked, pulverulent, ruptured epidermis inconspicuous, orange-yellow. Uredinia hypophyllous, scattered or loose groups, minute, round, orange-yellow, pulverulent 0.2-0.3 mm;paraphyses clavate, erect or incurved, wall thin, hyaline;urediniospores globose, sub-globose, obovate, broadly ellipsoid or obovoid, 12-25 x 13-20 µm;walls 1-1.5 µm thick, densely and coarsely echinulate, hyaline, contents orange-yellow or pale-yellow. Telia hypophyllous, scattered or gregarious, minute, round or irregular, 0.2-0.4 mm diameter, pulverulent, black;teliospores cylindrical, 2-6-septate, 35-111 x 18-27 µm, rounded at the apex, not constricted at the septa, chocolate-brown, smooth, apical papilla none, not or slightly thickened at the apex, two to three germ pores in each cell;pedicels hyaline, persistent, approximately 144 µm long. See Wei (1988) and Hiratsuka et al. (1992) for more detailed descriptions.
There is little published information on this plant pathogenic fungus, which is limited to parts of Asia. It infects Rubus spp., which exist in other regions of the world with similar environmental conditions;therefore this species may pose a threat to native or agricultural plants if introduced.
Spermogonia not seen. Aecia hypophyllous or petiolicolous, occasionally on fruits or young shoots, generally elongated on veins of leaves, petioles and shoots, up to 2 cm long, pulvinate, finally somewhat pulverulent, rupturing through epidermis, orange-yellow;paraphyses none;aeciospores globose, subglobose or ellipsoid, 20-30 x 15-22 µm, walls verrucose, 2.0-3.0 µm thick, nearly hyaline, contents orange-yellow. Uredinia hypophyllous, scattered or in small groups, minute, 0.1-0.6 mm diameter, orange-yellow to pale-yellow, pulverulent;paraphyses clavate, erect or incurved, 25-65 x 10-18 µm, hyaline, walls smooth, 1.0-2.5 µm thick;urediniospores globose, subglobose, broadly ellipsoid or obovoid, 18-27 x 15-21 µm;walls 2-3 µm thick, verrucose, hyaline;contents orange-yellow. Telia hypophyllous, scattered or gregarious, minute, round or irregular, 0.2-0.4 mm diameter, pulverulent, black;teliospores cylindrical, (3-)6-7(-9)-septate, 65-126 x 20-30 µm, rounded at apex, not constricted at septa, walls 2.4-4.0 µm thick, yellowish-brown, minutely verrucose (smooth, Hirastuka, 1992), apical papillae conical, up to 8-10 µm long with three germ pores in each cell;pedicels hyaline, persistent, 60-129 µm long. See Wei (1988) and Hiratsuka et al. (1992) for more detailed descriptions.
There is little published information on this plant pathogenic fungus, which is limited to parts of Asia. It infects Rosa spp., which exist in other regions of the world with similar environmental conditions, therefore this species may pose a threat to native or agricultural plants if introduced.
Aecia forming a large dense cushion on petioles, stems or fruits, and lower surface of leaves often causing conspicuous deformation, pulvinate, more or less pulverulent, bright orange-yellow;aeciospores sub-globose, broadly ellipsoid or somewhat angular, 20-28 x 16-22 µm, minutely verrucose, 2.0-3.0 µm thick, hyaline, walls orange-yellow;paraphyses numerous, clavate, 50-85 x 14-20 µm, walls smooth, uniformly thin, nearly hyaline. Uredinia hypophyllous, scattered or in groups, minute, 0.2-2.0 mm diameter, pale-yellow, pulverulent;urediniospores globose, sub-globose, obovate, or broadly ellipsoid, 18-25 x 15-24 µm, walls 1.5-3.0 µm thick, hyaline, finely verrucose, germ pores obscure, numerous, scattered;paraphyses clavate, 54-150 x 9-20 µm, erect or incurved, wall 1.5 µm thick;hyaline, sometimes slightly thicker at apex, up to 3.5 µm. Telia hypophyllous, scattered or gregarious, round or sub-round, 0.4-1.0 mm diameter, pulverulent, reddish-brown;teliospores cylindrical, (2-)4-6(-9)-septate, 60-138 x 32-47 µm, rounded at apex, walls 4-7 µm thick, yellowish-brown, coarsely verrucose with sub-hyaline tubercles, apical papilla obscure, up to 5 µm long, with three germ pores in each cell;pedicels hyaline, persistent, 45-168 µm long. See Wei (1988) and Hiratsuka et al. (1992) for more detailed descriptions.
There is little published information on this plant pathogenic fungus, which is limited to parts of Asia and the Russian Far East. It infects Rosa spp., which exist in other regions of the world with similar environmental conditions;therefore this species may pose a threat to native or agricultural plants if introduced.
Uredinia hypophyllous, scattered or in small groups, minute, round, yellow, pulverulent, 0.1-0.5 mm diameter;paraphyses clavate, 45-65 x 12-20 µm, wall 1.0-1.5 µm thick, hyaline, not or slightly thickened at apex;urediniospores globose, subglobose, obovate, or ellipsoid, 18-34 x 11-22 µm;walls 1.0-2.0 µm thick, minutely echinulate, germ pores obscure. Telia hypophyllous, scattered or gregarious, minute, round or irregular, 0.4 mm diameter, pulverulent, blackish-brown or black;teliospores cylindrical, (3-)6-7(-8)-septate, 60-135 x 22-30 µm, rounded at apex, not constricted at septa, walls 2.5-3.5 µm thick, chocolate-brown, minutely and closely verrucose with subhyaline tubercles, three germ pores in each cell;pedicels hyaline, persistent, up to 180 µm long. See Wei (1988) and Hiratsuka et al. (1992) for more detailed descriptions.
There is little published information on this plant pathogenic fungus, which is limited to parts of China and Japan. It infects Rubus spp., which exist in other regions of the world with similar environmental conditions, therefore this species may pose a threat to native or agricultural plants if introduced.
Spermogonia on current-year needles, amphigenous, subcuticular, hemispherical or conical, with flat hymenia, 85-150 µm diameter, 55-75 µm high, yellow-orange changing to brown;spermatia oblong-ellipsoid to ellipsoid, 4.0-5.0 x 1.5-2.0 µm, colourless. Aecia on current year needles, hypophyllous, cylindrical, 0.2-0.3 mm wide, 0.5-1.5 mm long, orange;peridial cells colourless, firm, rupturing at the apex;peridial cells oblong-ellipsoid to ellipsoid, 30-93 x 12-23 µm, overlapping, inner walls 2.0-2.5 µm thick, verrucose with striae, outer wall 1.5-2.0 µm thick, finely verrucose;aeciospores ellipsoid, obovate or subglobose, 20-27 x 13-20 µm, densely verrucose, occasionally with a reticulum-like area resulting from fused verrucae, 0.5-1.5 µm high, contents yellow. Uredinia hypophyllous, subepidermal, scattered, or rarely grouped, often thickly, scattered over the whole leaf surface, round, minute, 0.1-0.2 mm diameter, pale-yellow, at least somewhat pulverulent;peridia hemispherical, delicate, rupturing at apex;upper peridial cells small, isodiametrically to irregularly polygonal, 8-22 µm wide, lateral ones radially elongate, walls of peridial cells thin, 1-2 µm thick, smooth, nearly colourless;ostiolar cells globose or ellipsoid, walls rather thick, 2-4 µm, smooth, colourless;urediniospores obovate, ellipsoid or oblong, 18-27 x 10-16 µm, walls 1.2-1.5 µm thick, uniformly echinulate, nearly colourless, four to seven germ pores, bizonate, contents orange-yellow. Telia hypophyllous, subepidermal, minute, in dense clusters limited by veins, brownish-yellow;teliospores intercellular, solitary or grouped, often compacted laterally under epidermis, oblong or polygonal, 1-7-septate, 18-30 x 12-24 µm, smooth, pale-brownish. Basidiospores globose, 5-8 µm diameter, cytoplasm pale-yellow. See Kaneko and Hirastuka (1981) and Hirastuka et al. (1992) for more detailed descriptions.
There is little published information on this plant pathogenic fungus, which has limited geographic distribution. As hosts exist in other regions of the world with similar environmental conditions, this species may pose a threat to native or agricultural plants if introduced.
R. armeniacus is a perennial woody shrub in which individual canes can reach 6-12 m horizontally and 3 m vertically. Leaves are toothed and typically compounded with five leaflets but atypically or on fruiting branches can be tri- or unifoliate. Leaf blades are 3-12 cm long, ovate to orbicular and dark green in colour. Flowers are white to rose coloured and have five transversely arranged petals. The flowers form in groups of three to 20 in terminal panicles. The fruit are less than 2 cm aggregates of black, shiny, roundish drupelets. Each drupe contains a single, hard, flattened seed (Soll, 2004;Francis, 2014;Ensley, 2015).
R. armeniacus is a perennial shrub native to Armenia. It was introduced outside of its native range as a cultivated crop for the production of sweet fruits. It soon escaped cultivation and has since naturalized in many temperate areas around the world. R. armeniacus can reproduced both vegetatively and by the production of seed, which can be transported to new locations after ingestion by birds. This species is highly invasive and can form impenetrable thickets which have a negative impact on native flora and fauna. A PIER risk assessment gave this species a high risk score of 24 (PIER, 2015). In addition to this, it has been reported as highly invasive in Central Europe (von Raab-Straube and Raus, 2015) and has been identified as one of the 10 most problematic invasive plants or bryophytes in Sweden (Torbjorn et al., 2015) and noted as a threat to vegetation in Pannonian sandy habitats in Hungary (Király et al., 2014).
A small tree, commonly reaching 3-15 m tall and 10-35 cm in bole diameter;and older trees may reach 20 m tall and 50 cm in diameter. Form varies from shrubby and highly branched in subsp. leucocephala to arborescent with a short clear bole to 5 m, upright angular branching and an open, rounded crown in subsp. glabrata. Bark is mid grey-brown with shallow rusty orange-brown vertical fissures;slash reddish. Leaves bipinnate with 4-9 pairs of pinnae per leaf and 13-21 pairs of leaflets per pinna. The leaflets are small, 9-21 mm long, 2-4.5 mm wide, linear-oblong or weakly elliptic, acute at the tip, rounded to obtuse at the base and glabrous except on margins, with a concave, cup-shaped, elliptic petiole gland. Flowers arranged on compact globose heads, the flower heads in groups of 2-6 in leaf axils arising on actively growing young shoots, the leaves developing simultaneously with the flowers, the heads 12-21 mm in diameter with 100-180 flowers per head, the flowers white. Hairy anthers (visible with a hand lens) distinguish Leucaena from all other mimosoid legume genera. Pods are 9-19 cm long, 13-21 mm wide, linear-oblong and flat with papery pod walls, mid- to orange-brown, glabrous and slightly lustrous (subsp. glabrata and subsp. ixtahuacana), or densely covered in white velvety hairs (subsp. leucocephala), arranged in clusters of 3-20, and occasionally up to 45, per flower head.
P. reticulata belongs to the poeciliids, a group of small freshwater fishes with internal fertilisation and viviparous reproduction. P. reticulata has clear sexual dimorphism. Males are 25-35 mm (SL) and have conspicuous polymorphic colour patterns consisting of combinations of black, white, red-orange, yellow, green, iridescent spots, lines and speckles. Males have a gonopdium;a slender, modified anal fin used as an intromittent organ, whereas the anal fin of females is rounded. Females are uniform silver grey, and are larger and deeper bodied than males (40-60 mm SL). Juvenile fish resemble females, and are independent from birth.
P. reticulata is a prolific livebearing fish species, producing between 20 and 40 young after a gestation period of four to six weeks, and is able to tolerate a wide range of aquatic environments and conditions. It is native to parts of the Caribbean and northern South America, but it has been widely introduced throughout temperate and tropical regions originally for mosquito control, later as a popular species in the commercial aquarium trade. Further accidental introductions via release of unwanted pets and escape from aquaculture facilities are likely, and eradication of established populations is extremely difficult without broad scale damage to the aquatic environment and biota.
O. aurantiaca is an inconspicuous, perennial succulent shrublet which seldom exceeds 0.5 m in height in open pasture but can reach up to 2 m when supported in vegetation. Plants consist of one to 100 or more spiny, sausage-like, fleshy segments or joints (also known as cladodes). These are 50 to 200 mm long (but may be longer when growing under shade) and 10 to 30 mm wide. Young segments are bright green and flattened whereas older joints are often cylindrical with a corky surface. Segments covered by soil may lose thorns and resemble an underground tuber. If above-ground parts die, or are removed, plants may grow from these underground segments. Green segments take on the function of true leaves that are only present on newly formed segments and fall away within a few months. During periods of drought, or when exposed to direct sunlight, segments take on a more reddish to purplish colour. Joints are easily detached from the parent plant and in wet conditions quickly take root when in contact with the soil surface. Flowers are bright yellow (not orange as is suggested by the species name). Fruit are initially green but are red to purple and club-shaped with age. Each fruit may contain several sterile seeds. Fruit can also take root, in a similar way to segments, when falling to the ground. Reproduction of this cactus is entirely vegetative. Sharp spines arise in groups from areoles, which also contain minute thorns or glochids. Long spines have minute, backward-directed barbs at their extremities. These can hook onto passing objects, mainly animals, facilitating dispersal of isolated joints.
O. aurantiaca has shown itself to be a serious invasive weed on natural grasslands in Australia and South Africa for over a hundred years, reducing carrying capacity, injuring livestock and reducing the value of animal products. It was introduced as an ornamental species and spread rapidly via dispersal of vegetative parts. However, introduction of cochineal and the cactus moth as biological control have reduced populations in infested areas to scattered plants or patches which now have mostly only a nuisance value. Nonetheless, there is a risk of further introduction into new areas via the trade in ornamental succulents and/or its escape where already present.
Plants are sprawling or erect, much-branched succulent shrubs reaching a height of 2 m. The cladodes (stems) are green to bluish-green, flattened, and about 10-25 cm long and usually 7.5-15 cm broad. From the areoles develop the stout, slightly curved yellowish spines, varying in numbers from entirely absent to groups of one or two or more, normally clusters. Clochids (spine clusters) are yellow and relatively few, up to 5 mm long in the spinier var. dillenii. The flowers are bright yellow and typically cactus-like, appearing during the summer months (Benson, 1982). The species is best identified by its typical pear-shaped to spherical fruit, purple-coloured at maturity, 4-6 cm long and 2.5-3 cm in diameter. Its outer surface is smooth and spineless except for a few glochids imbedded in the small areoles. The pulp is intense purple in colour and sour tasting and contains about 60 hard-coated seeds. Older plants develop woody stems which provide support to the larger plants.
O. stricta, native from Ecuador to the USA, was introduced as an ornamental and has spread widely, mainly in southern Africa and Australia, but also more recently in the Mediterranean basin and in disturbed areas in its native Caribbean. Successful biological control programmes have, however, severely reduced the spread of this species in many areas where introduced, though there continues to be a risk of further introduction through the nursery trade.
Cherimoyas are erect trees, 3-10 m tall, often low-branched and somewhat shrubby or spreading. The briefly deciduous to semi-deciduous (just before spring flowering) leaves are ovate to ovate-lanceolate, sometimes obovate or elliptical, 12-20 cm x 8 cm, persistently brownish velvety-tomentose beneath. They are alternate, 2-ranked, with minutely hairy petioles, slightly hairy on the upper surface, velvety on the underside. Flowers are fragrant, extra-axillary, often opposite a leaf at the base of a branchlet, usually solitary but sometimes two or three grouped together on short nodding tomentose peduncles;outer three tepals oblong-linear, up to 3 cm long, greenish to pale yellow, marked with a purple spot at the base within;inner three tepals very small, reddish to purplish;androecium consisting of numerous free fleshy stamens, spirally arranged on the basal part of a conical receptacle;gynoecium comprising numerous free pistils on the upper part of the receptacle. Fruit is a syncarp or pseudocarp formed by the fusion of the carpels and the receptacle into a fleshy mass, variable in shape and appearance, from heart-shaped with surface bearing protuberances to spheroid or ovoid with the surface covered with 'U'-shaped areoles or rather smooth, 10-20 cm long and up to 10 cm in width, weighing on average 150-500 g, but extra large specimens of 2.7 kg or more have been reported;pulp white, edible, easily separable from the seeds. The skin may be smooth with fingerprint-like markings or covered with conical or rounded protuberances. The fruit is easily broken or cut open, exposing the snow-white, juicy flesh of pleasing aroma and delicious, subacid flavour. It contains numerous hard, brown or black, bean-like, glossy seeds, 1.25-2 cm long. The fruit is composed of an exocarp (fruit skin), occupying between 15 and 25% on a weight basis, an edible mesocarp (pulp and thalamus), varying between 65 and 80%, and seeds, ranging from 3 to 10%. Seeds usually obovate, obliquely truncate, somewhat compressed, with a thin, membranous, brown, wrinkled testa.
A. cherimola is a tree of American origin that has been cultivated in tropical and temperate regions around the world for its edible fruit. It is listed as a “cultivation escape, environmental weed, naturalised, weed” in the Global Compendium of Weeds (Randall, 2012) and is known to be invasive in places both within and beyond its native range including Easter Island, the Galapagos, Hawaii, and New Zealand (PIER, 2014). A risk assessment gave the species a low invasive risk score of -4, but excluded several invasive traits in this score such as its known status as a garden/agricultural/environmental weed and naturalization beyond its native range (PIER, 2014). The species reproduces by seeds but can be propagated by grafting (Janick and Paull, 2008).
A. densiflorus is a spiny perennial plant, persisting and spreading by fleshy rhizomes and roots bearing white tubers 2-3 cm long. Stems up to 2 m long are glabrous, green to brown, much-branched and ‘leafy’ but the clusters of flattened ‘leaves’ are in fact cladophylls about 2 cm long, 2-3 m wide. True leaves are represented by small scales at the base of the cladophylls. The stems also bear scattered straight spines, about 5 mm long, just below each branch. Flowers are in groups at the stem apices, white or pale pink, bell-shaped, with a corolla of 6 tepals and orange anthers. Fruit is a red berry 5-8 mm in diameter, containing one or a few seeds 3-4 mm in diameter (Parsons and Cuthbertson, 1992).
A. densiflorus is a spiny perennial plant, commonly found in savanna thickets in its native environment in eastern Africa and South Africa. It has been widely introduced globally as an ornamental and has subsequently naturalised and become a problem in a number of countries, including the USA and Australia. The plant forms dense spiny mats, up to 2 m high in light and sandy soils, suppressing other ground flora and depleting the soil of nutrients and moisture. It may quickly invade disturbed sites in open sun or partial shade and can become a threat in coastal habitats, along river banks and in low fertility soils. It is among the most abundant invasive ornamental weeds of sandy beachfronts in Queensland, Australia and threatens natural vegetation on Lord Howe Island, Norfolk Island and a number of other islands in the Pacific Ocean. The risk assessment score for this plant in Australia is 3 (‘requiring evaluation’) and for the Pacific Islands it has a high score of 15. In Florida, USA it has been reported as displacing native ground cover, understory shrubs and the native wild coffee species Psychotria nervosa. It is also of sufficient concern for it to have been recommended for voluntary withdrawal from sale within the state (Wirth et al., 2004). In Hawaii, USA it is spreading along roadsides and invading secondary forest (PIER, 2008).
A. densiflorus is rarely a weed in any agricultural crop.
C. selloana is an erect perennial, tussock grass, up to 2-4 m tall and 1-2 m wide. The leaves are 1-3 m long and 3-8 cm wide, glaucous-green, with serrulate margins and a V-shaped cross-section. The leaves are contained in groups in an auricle-like sheath often glabrous at the base. Inflorescences consist of several large plumose light-violet to silver-white (30-130 cm) long, stiff panicles. It is a gynodioecious species (i.e. it has hermaphrodite plants and female plants). It forms numerous 1.5 cm spikelets, containing six florets in female plants and three in hermaphrodite plants. Florets are less than 1 cm long, glumes are white or membranous, the lemma is long and hairy, awns are less than half a centimeter long and the stigmas are exerted. Seeds are not easily separated from the racilla (DiTomaso, 2000) and they weigh, on average, 2.74 x 10 -4 g (Lambrinos, 2002).
C. selloana (pampas grass) is an erect perennial, tussock grass, up to 2-4 m tall and 1-2 m wide. It has large (1-3 m), glaucous-green leaves with serrulate margins. Inflorescences consist of several large plumose light-violet to silver-white panicles producing thousands of tiny wind-dispersed seeds. This South American grass has been introduced in temperate and subtropical areas mainly as an ornamental. It has also been introduced for erosion control and as a barrier or windbreak. It is listed as one of the worst invader taxa in Europe (DAISIE, 2009) and as a noxious species in Western Australia (Parsons and Cuthbertson, 2001).
In New Zealand and Australia it affects pine plantations (Parsons and Cuthbertson, 2001).
Host Plants and Other Plants Affected
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Biology and Ecology
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Genetics 2n = 72 (Lambrinos, 2002). Mean total gene diversity (Ht) for 10 microsatellite loci in 650 invasive individuals, averaged over 29 populations sampled in California, USA, is 0.590 compared to 0.622 from 275 cultivated plants of different varieties (Okada et al., 2007). It does not hybridize with related taxa. Reproductive Biology It is a gynodioecious species, that is, some plants produce hermaphrodite flowers and others produce only female flowers (Connor, 1973). Functionally, hermaphrodite plants act only as pollen donors and therefore seed production on hermaphrodite plants is very low. A panicle from a female plant can produce more than 50,000 seeds;whereas seed production in hermaphrodite plants is one order of magnitude lower (Domènech, 2005). A female plant can produce more than one million viable wind-dispersed seeds. Seeds lack dormancy (Costas-Lippmann, 1976). Seed viability between the two sexes is also different;it is five times greater in seeds from female plants than from hermaphrodites. Seeds germinate under a wide range of environmental conditions, yet germination rate can be improved under shading, in sandy soils and with high water availability (Domènech and Vilà, 2008a). Vegetative reproduction can occur when tillers are fragmented and receive adequate moisture. However, it hardly occurs in nature, but plant propagation through the division of mature plants has traditionally been used for ornamental purposes (DiTomaso, 2000). Physiology and Phenology It flowers in late summer, and hermaphrodite panicles appear 1 or 2 weeks before female panicles (Parsons and Cuthbertson, 2001). Seed dispersal occurs in the autumn and seeds germinate in the early spring. In Mediterranean areas where this species has been introduced, summer drought and mammal herbivory are the major causes of seedling mortality (Lambrinos, 2002). Seedlings seem to be more resistant to water stress than similar coexisting perennial grasses because as water become scarce, C. selloana maximizes water uptake by increasing the R/S ratio and minimizes water loss by reducing specific leaf area (Domènech and Vilà, 2008b). Optimal temperature for seedling growth is 20ºC (Stanton and DiTomaso, 2004). Seedling survival and growth is enhanced by protection from direct light exposure, and soil disturbance at any seral stage and in any habitat type (Lambrinos, 2002;Domènech and Vilà, 2006). Associations In Argentina, wet grasslands dominated by C. selloana are refuges for small mammals such as the rare sigmodontine rodent Deltamys kempi (Teta et al., 2007). In New Zealand, the rare hyphomycete (Zygosporium bioblitzi) has been found on dead, attached leaves (McKenzie et al., 2007). Environmental Requirements In its introduced range, C. selloana can be found from sea level to around altitudes of 400 m. An analysis of soil characteristics across 27 populations along a 300 km area, found soil N ranging from 0.03-0.3 %, organic C from 0.09-4.6 % and pH 7.4-8.5. Plant population density and the proportion of juvenile plants were positively correlated to percentage bare ground. Plant density was also negatively correlated with pH and richness of plant functional groups (Domènech and Vilà, 2007).
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BS - Steppe climate| Preferred
430mm and 860mm annual precipitation
Cf - Warm temperate climate, wet all year| Preferred
Warm average temp. 10°C, Cold average temp. 0°C, wet all year
Cs - Warm temperate climate with dry summer| Preferred
Warm average temp. 10°C, Cold average temp. 0°C, dry summers
Cw - Warm temperate climate with dry winter| Preferred
Warm temperate climate with dry winter (Warm average temp. 10°C, Cold average temp. 0°C, dry winters)
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Latitude North (°N)|Latitude South (°S)|Altitude Lower (m)|Altitude Upper (m)
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Mean annual temperature (ºC)
Mean maximum temperature of hottest month (ºC)
Mean minimum temperature of coldest month (ºC)
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Parameter|Lower limit|Upper limit|Description
Dry season duration|0|4|number of consecutive months with 40 mm rainfall
Mean annual rainfall|400|1100|mm;lower/upper limits
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Special soil tolerances
Means of Movement and Dispersal
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Seeds are very light and wind dispersed. Seed drop time is on average 0.22 m/sec (Lambrinos, 2002). Seeds can disperse to at least 40 m away from mother plants, and local wind direction determines the spatial distribution of seedlings (Saura-Mas and Lloret, 2005).
In cultural landscapes its spread is very much related to time because of pasture or agricultural field abandonment and distance to urban areas where it is planted as an ornamental (Domènech et al., 2005). Plant density in old fields can increase three fold in less than 5 years (Domènech et al., 2005). In northern, humid areas of Spain, population size can increase two fold in a year (Herrera and Campos, 2006).
When young the plant is an erect woody shrub that becomes scrambling or climbing and vine-like, with branches up to 10 m long. The spines occur in groups and are long and slender, on the branches they are short and curved, usually occurring in pairs or threes in the leaf axils. The stem has a mucilaginous sap. The alternate, waxy leaves are elliptic, oblong or ovate (3.2–10 cm long) and normally fleshy and succulent;if conditions are adverse they will become deciduous. The semi-transparent white, yellowish or pink-tinted flowers (2.5–4.5 cm across) have a sweet and pungent odour and are borne in terminal panicles. The calyx tube is prickly. The fruit is a round, oval or pyriform berry, lemon- or orange-yellow or reddish (1–2 cm wide), with a thin, smooth, leathery skin. The curling, leafy sepals of the calyx cover the fruit and fall when the fruit reaches maturity. Few spines are found on the fruit. When fully ripe, the white fruit pulp is juicy with a sub-acid to tart flavour and contains a few flat, thin, brown or black, shiny, soft seeds that are 4 mm long (Janick and Paull, 2008).
A group is a number of people or things that are located, gathered, or classed together.
A number of individual items or people brought together.