What is the Asian cycad scale?
By Chelsie Vandaveer
October 22, 2003
killerPlants Tendrils: ~~1~~2~~3~~4~~5~~
Suggested Reading: Click here.
Cycads are unique seed-bearing plants; in the genus Cycas, the seeds are borne along the edges of special leaves on the female plants. Seed ferns were the first plants to evolve the capability of reproducing by seeds. Ancestors of Cycas were somewhere close to second. The seed ferns have long been extinct; Cycas are the descendents of the longest continuous seed plant lineage on Earth.
Cycas survived the rise and fall of the dinosaurs. They survived the ice sheets of the Pleistocene. They are beautiful additions to the landscape; tough, drought-tolerant, and unusually resistant to pests. Until now.
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Close-up of a Cycas frond with a dense population of mostly male scales on the rachis (central leaf stem) and the larger females on the leaflets.
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The Asian cycad scale (Aulacaspis yasumatsui Takagi) was not discovered until 1972. The insects were found in Thailand as pests of Cycas growing there. But the scale is not a problem in Southeast Asia. It is thought native parasitoids keep the insects in check.
Sometime in the 1990s, cycad scale left Asia, possibly in a shipment of infested plants that slipped passed plant inspectors or on a specimen someone smuggled out of Thailand. In 1996, cycad scale was found in south Miami; it is now a problem in the Cayman Islands, Hawaii, Hong Kong and this author's garden. ("Aulacaspis yasumatsui Takagi", T.J. Weissling and F.W. Howard, University of Florida Institute of Food and Agricultural Sciences, 1999)
The sexes of cycad scale are distinctly dimorphic. The males are tiny and elongate; the females are much larger and somewhat pear-shaped. Cycad scales live in extremely dense populations with as many as three thousand inhabiting a square inch of the plant's surface. ("Asian Cycad Scale", Dave Palmer and JoAnn Hoffman, University of Florida Extension Service, Hillsborough County)
The scales will completely cover a cycad, even underground. The crawlers can establish themselves on the caudex (specialized storage stem) as far underground as 60 centimeters (24 inches). If they are not controlled, the scales kill the cycad in about a year.
Florida Entomologist has an in-depth article on this 'new' pest to Florida landscaping by Forrest W. Howard, Avas Hamon, Michael Mclaughlin, Thomas Weissling, and Si-lin Yang. To learn more about this scale, click on the link:
http://www.fcla.edu/FlaEnt/fe82p14.htm
killerPlants Tendrils: ~~1~~2~~3~~4~~5~~
Suggested Reading:
What are soft brown scales? Renfield's Garden - March 19, 2003
What was the scarlet of the Aztecs? Renfield's Garden - July 24, 2002
What is shellac? Renfield's Garden - May 28, 2003
A medical mystery in Guam Herbal Folklore - May 31, 2004
King Sago (Cycas revoluta) Plant of the Week - May 24 2004
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