C. odorata is a tree up to 20 m high and with a trunk diameter than can exceed 2 m. Odour is a characteristic of this plant, leaves smelling strongly of garlic or onions, and flowers having a strong malty smell. L eaves are very long, up to 80 cm long, with (5-) 6-7 (-14) pairs of leaflets;leaflets ovate to lanceolate, acute to rounded at base, acute, acuminate or obtuse at tip, 8-20 cm long, 2.5-5.5 (-8) cm broad, generally glabrous. The large and much-branched inflorescences bear numerous small, five-part, symmetrical greenish-white flowers. Flowers are 6-9 mm long;petals greenish-cream in bud becoming white after opening. Fruits are 2.5-4.5 cm long, winged, and septicidally 5-valved. Seeds are flat, chestnut-brown, 20-25 mm long and 6 mm broad including the wing (adapted from PIER, 2008).
FACTSHEETS FOR FARMERS www.plantwise.orgCreated in Pakistan, June 2014 Chemical control of downy mildew of onion Recognize the problem Downy mildew is a disease that is caused by a fungus. The fungus cannot be seen by the naked eye but when the problem is severe, you can see the symptoms of the disease on the plant leaves. Infected bulbs are usually small compared to healthy bulbs. The disease causes leaves to turn pale green or yellow, and curl downwards. A greyish-violet downy growth develops on infected leaf tissue. The disease is more common on seed crops than bulb crops. Downy...
FACTSHEETS FOR FARMERS www.plantwise.orgCreated in Pakistan, June 2014 Drying Tubers to Control Neck and Bulb Rot of Onion and Garlic Recognize the problem Neck and bulb rot of onion and Garlic generally appears during storage but the infection may also originate in the field. The symptoms begin at the neck of the onion. The affected tissue softens, becomes water soaked and turns brown. The infected plants may be stunted with drying outer margins. Background The fungus lives on dead onion and garlic tissues or in the soil. It grows better in moist weather and can spread through the...
FACTSHEETS FOR FARMERS www.plantwise.orgCreated in Zambia, July 2014 Intercrop cabbage with onion against aphids Recognize the problem Aphids are very small soft-bodied roundish insects of about 1 to 3 mm in length. The body colour varies from yellow to green to brown to purple. They live on most fruits, vegetables and ornamentals. Aphids feed by sucking sap from the plant. In cabbage, they are found on the leaves where they feed and cause damage. The signs of aphid infestation include curling or distortion of leaves, production of a sugary substance called honeydew, which leads to...
FACTSHEETS FOR FARMERS www.plantwise.orgCreated in Ethiopia, August 2014 Using neem seed for managing thrips in onion Recognize the problem Thrips are very small insects, about the size of a flea and just about visible to the naked eye. Immature stages referred to as nymphs are either yellow or white. Older individuals are yellowish-brown and move quickly. They feed by damaging the surface of the leaves and sucking the sap that exudes from the leaves. They often gather along the leaf veins. Onion leaves damaged by thrips are silvery or have tiny brownish marks or spots. They may be...
FACTSHEETS FOR FARMERS www.plantwise.org Created in Sri Lanka , October 2013 Seed Bulb Treatment on Onion Recognize the problem Many of the fungal diseases affecting onion are seed borne. Preventive actions are always better than curative actions to minimize economic loss. Therefore, seed treatment before establishment of the crop is essential. Background Seed treatments can often be used to control pathogens that occur on or in the seeds. By treating the bulbs before planting, disease infection can be prevented as all of the fungal inoculum...
FACTSHEETS FOR FARMERS www.plantwise.org Created in Bolivia , July 2012 Purple blotch in onions Recognize the problem Purple blotch is one of the diseases that cause most damage to the onion. It causes deep white spots with a yellow halo and a purple or red centre. In humid climates, the spot surface becomes dark or coffee-colored. Within 2 to 3 weeks, these spots surround the leaves. In the bulbs, the infection appears close to maturity. It appears as a watery rot on the neck, penetrating towards the centre of the bulb. Background The purple...
FACTSHEETS FOR FARMERS www.plantwise.org Created in Honduras , November 2012 Onion thrip control Recognize the problem The thrips develop in the onion as well as in weeds and on the soil. Thrips are very small, about the size of a grain of sand, and are hidden in the leaf axils of onion. While feeding, they scrape the leaf surface and leave a free entrance to fungal diseases. Young adults are transparent white but soon become dark and coffee-coloured. Background The thrip lays its eggs on the forage and on volunteer plants. The thrips eat a...
FACTSHEETS FOR FARMERS www.plantwise.org Created in Tanzania , October 2012 Thrips management in tomatoes Recognize the problem Thrips ("Vithiripi" in Swahili) are very small and thin insect pests (1.5 mm long). They are light grey-greenish, but difficult to see. Thrips cause tiny scars on leaves and fruits. Damaged leaves become papery and may curl and drop prematurely. Thrips usually attack during the flowering stage of tomatoes. Background Thrips pierce leaves and soak liquid out of plants. Therefore plants loose more water than normal and...
FACTSHEETS FOR FARMERS www.plantwise.org Created in Honduras , November 2012 "Burned tip" or downy mildew in onions Recognize the problem Downy mildew is a fungus that affects all stages of the onion plant. It produces burns and coffee-colored spots on the leaves, generally starting at the tips and moving downwards. At the beginning, it can be confused with injuries caused by chemicals and mechanical damage. A severe attack may reduce the yields and the product quality almost completely. Background This fungus is transmitted through spores that can survive on the soil, attacking new crops. It...
FACTSHEETS FOR FARMERS www.plantwise.org Created in Tanzania , September 2013 Thrips management in onion Recognize the problem Thrips (“ Vithiripi ” in Swahili) are very small, only 1.5 mm long, thin insect pests. They are light grey-greenish, but very difficult to see. They suck on onion leaves starting on leaf bases. Leaf surfaces become covered with silvery feeding leaf spots or patches. You can usually see these along the inner angles of the leaves. When damage is severe, these patches can occupy most of the leaf surface....
FACTSHEETS FOR FARMERS www.plantwise.org Created in Tanzania , September 2012 Soap sprays against thrips in onion Recognize the problem Thrips are very small, only 1.5 mm long, elongate insect pests. They are light grey-greenish, but difficult to see. They suck on the leaf bases of onion. Infested onions develop silvery leaf spots or patches along the inner angles of onion leaves. Infestation causes premature wilting, delay in leaf development and distortion of leaves of young shoots. Under heavy infestations, buds and flowers are attacked...
FACTSHEETS FOR FARMERS www.plantwise.org Created in India , November 2012 Management of Uniformity in Size of Bulbs in Onion Recognize the problem Non-uniformity in bulb size of onion is a very big problem which leads to economic loss to the farmers. Non-uniform bulbs are difficult to store for marketing. The difference in size does not attract a good value for the crop in the market. Hence, the uniformity in size of onion bulbs is very important. Background Uniformity in maturity plays a very important role in bulb size and storage quality....
FACTSHEETS FOR FARMERS www.plantwise.org Created in Kenya , December 2012 Tomato Spotted Wilt Virus on Tomato Recognize the problem The tomato fruit shows yellow or pale red ring patches and some areas of the tomato may die. Purplish-brown spots appear on young leaves. Older leaves turn brown and drop. The whole plant becomes stunted and wilted. The tip of leaves may dieback and leaves may cup downwards. Background This virus is carried by thrips. Its host range includes broadleaf and grassy plants including onions. The virus persists from year...
FACTSHEETS FOR FARMERS www.plantwise.org Created in Kenya , December 2012 Bugs on Mango Recognize the problem The most common bugs found in mango orchards include the Helopeltis bugs also called mosquito bugs, Tip wilters and the Coconut bug. Both young and adult bugs feed on young flesh on the mid-vein of young leaves, or on flower stalks, causing wilting and death of new growth. They also feed on young fruits causing immature fruits to become deformed and fall. Background When bugs are disturbed they either fly away or fall to the ground or to...
FACTSHEETS FOR FARMERS www.plantwise.org Created in Kenya , December 2012 Aphids on Brassica Recognize the problem Cabbage aphids are green to pale grey insects with a white, waxy coating. They are soft-bodied insects found in groups, often underneath the leaves. They cause misshapen leaves, spread virus diseases and produce a sugary substance called honeydew. This substance sticks on the leaves and encourages a black fungal growth. The feeding of the aphids causes leaves to curl around the pests, making them harder to reach with pesticide...
KNOWLEDGE FOR LIFE Onion disorders CABI PEST AND DISEASE PHOTOGUIDE TOIntroduction This photo booklet has been produced by the CABI-led Plantwise programme (www.plantwise.org) to aid extension officers and other plant health advisors in diagnosing the most common pests, diseases and abiotic problems of coffee around the world. The symptoms presented on a real plant sample can be compared with the photos in this guide to identify possible causes. The booklet is organized into two broad sections, one showing the common insect pests that attack the crop and the other showing the...
Plant Pathology Fact SheetPP-124Florida Cooperative Extension Service/ Institute of Food and Agricultural Sciences/ University of Florida/ Christine Waddill, Dean Botrytis Leaf Blight and Purple Blotch of Onions in Florida Tom Kucharek, Extension Plant Pathologist, Plant Pathology Department, Uni- versity of Florida, Gainesville FL 32611.1996, Revised January 2000. Onions are grown throughout Florida in small-to medium-sized commercial plantings or in home gardens. Numerous plant diseases occur in the roots, bulbs, and leaves of onion. Purple blotch and botrytis leaf blight are the most...
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Allium ascalonicum L.
Cepa rotunda Dod.
Allium esculentum Salisb.
Allium porrum cepa Rehb.
P. hysterophorus is an erect, much-branched with vigorous growth habit, aromatic, annual (or a short-lived perennial), herbaceous plant with a deep taproot. The species reproduces by seed. In its neotropical range it grows to 30-90 cm in height (Lorenzi, 1982, Kissmann and Groth, 1992), but up to 1.5 m, or even 2.5 m, in exotic situations (Haseler, 1976, Navie et al., 1996). Shortly after germination the young plant forms a basal rosette of pale green, pubescent, strongly dissected, deeply lobed leaves, 8-20 cm in length and 4-8 cm in width. The rosette stage may persist for considerable periods during unfavourable conditions (such as water or cold stress). As the stem elongates, smaller, narrower and less dissected leaves are produced alternately on the pubescent, rigid, angular, longitudinally-grooved stem, which becomes woody with age. Both leaves and stems are covered with short, soft trichomes, of which four types have been recognized and are considered to be of taxonomic importance within the genus (Kohli and Rani, 1994).;Flower heads are both terminal and axillary, pedunculate and slightly hairy, being composed of many florets formed into small white capitula, 3-5 mm in diameter. Each head consists of five fertile ray florets (sometimes six, seven or eight) and about 40 male disc florets. The first capitulum forms in the terminal leaf axil, with subsequent capitula occurring progressively down the stem on lateral branches arising from the axils of the lower leaves. Thousands of inflorescences, forming in branched clusters, may be produced at the apex of the plant during the season. Seeds (achenes) are black, flattened, about 2 mm long, each with two thin, straw-coloured, spathulate appendages (sterile florets) at the apex which act as air sacs and aid dispersal.
P. hysterophorus is known to reduce the yield of various crops and to compete with pasture species in various countries. However, the yield loss and specific effects on the crops have not been quantified in all countries (Rubaba et al., 2017).;In Australia, the main impact of P. hysterophorus has been in the pastoral region of Queensland, where it replaces forage plants, thereby reducing the carrying capacity for grazing animals (Haseler, 1976, Chippendale and Panetta, 1994). Serious encroachment and replacement of pasture grasses has also been reported in India (Jayachandra, 1971) and in Ethiopia (Tamado, 2001, Taye, 2002). The weed is also able to invade natural ecosystems, and has caused total habitat changes in native Australian grasslands and open woodlands (McFadyen, 1992).;In India, the yield losses are reported as up to 40% in several crops and a 90% reduction of forage production (Gnanavel, 2013). P. hysterophorus is now being reported from India as a serious problem in cotton, groundnuts, potatoes and sorghum, as well as in more traditional crops such as okra (Abelmoschus esculentus), brinjal (Solanum melongena), chickpea and sesame (Kohli and Rani, 1994), and is also proving to be problematic in a range of orchard crops, including vineyards, olives, cashew, coconut, guava, mango and papaya (Tripathi et al., 1991, Mahadevappa, 1997, Gnanavel, 2013).;Similar infestations of sugarcane and sunflower plantations have recently been noted in Australia (Parsons and Cuthbertson, 1992, Navie et al., 1996), whilst in Brazil and Kenya, the principal crop affected is coffee (Njoroge, 1989, Kissmann and Groth, 1992). In Ethiopia, parthenium weed was observed to grow in maize, sorghum, cotton, finger millet (Eleusine coracana), haricot bean (Phaseolus vulgaris), tef (Eragrostis tef), vegetables (potato, tomato, onion, carrot) and fruit orchards (citrus, mango, papaya and banana) (Taye, 2002). In Pakistan, the weed has been reported from number of crops, including wheat, rice, sugarcane, sorghum, maize, squash, gourd and water melon (Shabbir 2006, Shabbir et al. 2011, Anwar et al. 2012).;In Mexico, the species is reported as a weed in cotton, rice, sugarcane, Citrus spp, beans, safflower, sunflower, lentils, corn, mango, okra, bananas, tomato, grapes, alfalfa, chili peppers, luffa, marigolds and other vegetables and fruit orchards. It is also a weed in nurseries. In Argentina is reported as a weed of tobacco fields (CONABIO, 2018).;Gnanavel (2013) also reports the following detrimental effects of P. hysterophorus on crops: it inhibits nitrogen fixing bacteria in legumes, the vast quantity of pollen it produces (ca. 624 million/plants) inhibits fruit setting, it is an alternative host for viruses that cause diseases in crop plants, and it is an alternative host for mealy bugs.
The following description is from the Flora of China Editorial Committee (2016)
Erechtites hieraciifolius is a fast-growing, annual herb that is native to North, Central and South America and the Caribbean. It is recorded as an environmental and agricultural weed in areas both within and outside its native distribution. Mature plants can produce large amounts of wind-dispersed seed, facilitating the colonisation of new areas. It is adapted to grow in a wide range of disturbed anthropogenic habitats and can outcompete other species to form dense populations. It may also spread as a seed contaminant of crops. Currently, it is listed as invasive in Hong Kong, Hawaii, the Galapagos Islands, French Polynesia, Palau, US Minor Outlying Islands, New Zealand and Hungary. It is also considered a potential weed in Australia, where it is under quarantine.
E. hieraciifolius has been listed as a weed of the following crops: oat (Avena sativa), barley (Hordeum vulgare), maize (Zea mays), strawberry (Fragaria ananassa), onion (Allium cepa), carrot (Daucus carota), cranberry (Vaccinium macrocarpon), blueberry (Vaccinium spp.) and sugarcane (Saccharum officinarum);it is also a weed of fodder crops (e.g. Medicago sativa) and of mixed pastures (Darbyshire et al., 2012).