Taxonomic name: Aulacaspis yasumatsui Takagi
Common names: Asian cycad scale (Hawaii), cycad aulacaspis scale (CAS) (Florida, Guam), cycad scale (Hawaii), sago palm scale (Hawaii), snow scale, Thai scale
Organism type: insect
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.
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).
Infestations of CAS on cycads begin on the undersides of leaflets or at the base of the petiole. As the infestation progresses, scales also infest the upper surfaces of leaflets, the terminal portion of the cycad, the trunk and even roots and seeds/cones (Heu et al. 2003; Weissling et al. 1999; Haynes, pers. comm.). The leaves of infested cycads have a whitewashed or snow-covered appearance due to the numerous white scales. Plants that have been infested for some time will typically have chlorotic, yellow-brown leaves, as the continuous removal of plant sap by the scale will usually result in the death of the leaves (Heu et al. 2003). The scale can eventually form several layers, which include a high proportion of dead as well as live insects. Heavy infestations can consist of up to 3,000 scales per square inch in several layers (Weissling, 1999).
A simple way to tell if a plant has CAS, as opposed to other types of scale, is the speed in which it multiplies and the thickness with which it covers the plant. An infestation usually starts on the petioles near the crown of the plant, and works out from there. The plant will usually be totally covered within a couple of months (Broome, 2004).
Pinnaspis strachani, Pseudaulacaspis cockerelli
natural forests, urban areas
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).
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%.
Native range: Southeast Asia (Howard et al. 1999; Muniappan, 2005). According to Dr. Chandrashekara and Dr. A. Viraktamath of the Department of Entomology at the University of Agricultural Sciences in Bangalore, India, CAS has so far not been recorded in India. .
Known introduced range: USA (Florida, Hawai‘i, Georgia, Texas, Alabama, California, Louisiana, South Carolina), Cayman Islands, Puerto Rico and Vieques Islands, US Virgin Islands, Singapore, Hong Kong, Guam. Intercepted at the border in France. Intercepted at the border in New Zealand and eradicated.
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).
Integrated management: Research has indicated that maintaining Aulacaspis yasumatsui (cycad aulacaspis scale (CAS)) populations at a rate that does not threaten the health of plants requires multiple control measures (Wiese and Mannion, undated). The long-term solution may lie in biological control, however, in the short term it is necessary to control the pest on as many plants as possible by treating plants and preventing further spread (IFAS, 2005).
Please follow this link for management information and control options compiled by the ISSG.
The Cycad Aulacaspis Scale Pest Alert notification released by the IUCN SSC Cycad Specialist Group gives details on description, mode of attack, range, vulnerable species, images and control options.
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).
Reviewed by: F. W. Howard, Ph.D. Associate Professor of Entomology, University of Florida, IFAS. Fort Lauderdale Research & Education Center Florida USA
Jody Haynes, Secretary & Webmaster, IUCN Cycad Specialist Group, Miami, FL, USA
Principal sources: Howard et al. 1999. Aulacaspis yasumatsui (Hemiptera: Sternorrhyncha: Diaspididae), a scale insect pest of cycads recently introduced into Florida.
Weissling et al. 1999. Featured creatures: Cycad Aulacaspis Scale, Aulacaspis yasumatsui Takagi.
Compiled by: IUCN/SSC Invasive Species Specialist Group (ISSG) with support from the Terrestrial and Freshwater Biodiversity Information System (TFBIS) Programme (Copyright statement)
Last Modified: Sunday, 10 January 2010