Aulacaspis yasumatsui

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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Plant name|Family|Context
Ceratozamia|
Cycas|Cycadaceae
Cycas micronesica|Cycadaceae
Cycas revoluta (sago cycas)|Cycadaceae
Cycas rumphii|Cycadaceae
Cycas taitungensis|Cycadaceae
Cycas thouarsii|Cycadaceae
Dioon|Zamiaceae
Encephalartos|Zamiaceae
Encephalartos ferox|Zamiaceae
Encephalartos lebomboensis|Zamiaceae
Encephalartos longifolius|Zamiaceae
Encephalartos natalensis|Zamiaceae
Encephalartos paucidentatus|Zamiaceae
Encephalartos transvenosus|Zamiaceae
Encephalartos villosus|Zamiaceae
Macrozamia|
Microcycas|
Stangeria|
Stangeria eriopus|Stangeriaceae
List of Symptoms/Signs
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Sign|Life Stages|Type
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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Reproduction
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).
Lifecycle stages
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).
Natural enemies
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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).
Host (local):
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).
Pathway Causes
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Cause|Notes|Long Distance|Local|References
Hitchhiker|| Yes
Yes
Horticulture|| Yes
Yes
Nursery trade|| Yes
Yes
Pathway Vectors
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Vector|Notes|Long Distance|Local|References
Debris and waste associated with human activities|| Yes
Host and vector organisms|| Yes
Yes
Plants or parts of plants|| Yes
Yes
Wind|| Yes
Plant Trade
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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
Leaves
adults;nymphs| Yes
Pest or symptoms usually visible to the naked eye
Roots
adults;nymphs| Yes
Pest or symptoms usually visible to the naked eye
Stems (above ground)/Shoots/Trunks/Branches
adults;nymphs| Yes
Pest or symptoms usually visible to the naked eye
Plant parts not known to carry the pest in trade/transport
Flowers/Inflorescences/Cones/Calyx
Impact Summary
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Category|Impact
Animal/plant collections
Negative
Environment (generally)
Negative
Native flora
Negative
Rare/protected species
Negative
Impact
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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%.
Threatened Species
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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,
2011
Cycas revoluta (sago cycas)|LC (IUCN red list: Least concern)|Herbivory/grazing/browsing| ISSG,
2011
Cycas taitungensis|EN (IUCN red list: Endangered)| Taiwan|Herbivory/grazing/browsing| ISSG,
2011
Risk and Impact Factors
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Invasiveness
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
Impact outcomes
Host damage
Negatively impacts forestry
Threat to/ loss of endangered species
Threat to/ loss of native species
Negatively impacts animal/plant collections
Impact mechanisms
Herbivory/grazing/browsing
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).