Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
2/21/00
Contacts:
Donald Lewis, Extension Entomology, (515) 294-1101,
drlewis@iastate.edu
Elaine Edwards, Extension Communication Systems, (515)
294-5168, eedwards@iastate.edu
Yard and Garden Column for the Week Beginning Feb. 25
Asian Longhorned Beetle - A Tree's Worst Nightmare
By Donald R. Lewis
Extension Entomologist
Iowa State University Extension
Over the years a great many insects have immigrated to the United States either accidentally or with our help. Once present, these newcomers quickly establish and become serious pests. Think of the European corn borer, the Japanese beetle and the gypsy moth. To that list we can add one of the world's most destructive pests of trees, the Asian longhorned beetle. As documented by media coverage, the Asian longhorned beetle is a major economic, environmental and aesthetic threat to landscapes and woodlands.
The Asian longhorned beetle is native to China, Korea and Japan where it is known as a powerful killer of hardwood trees. So far, Asian longhorned beetle has not been found in Iowa. Infestations have been located in Chicago, Du Page County and Summit, Ill.; and Amityville and Brooklyn, N.Y. An infestation means there is a reproducing population of beetles killing trees.
Asian longhorned beetle probably traveled to the United States inside solid wood crating materials on ships delivering goods from China. Records indicate this has happened several times. Government inspectors have been watching for this insect and as of last summer, individual beetles had been detected as least 26 times at ports and warehouses throughout the United States. Each detection is an individual beetle found in association with wooden packing material and intercepted before an infestation occurred.
The beetles attack a wide variety of hardwood trees, including maples (all kinds), elm, birches, willows, green ash and probably others. Repeated attacks over a period of years are ultimately fatal to healthy, living trees and dispersal from an area of establishment can be rapid.
To make matters worse (if that is possible) there is no known cure. Infested trees must be cut down and destroyed to stop the infestation. Research on insecticide treatment is under way but not yet considered an effective alternative to tree and stump destruction.
Attractive Beetle
The name given to the Asian longhorned beetle in China is the "starry sky beetle." Adult beetles are up to an inch and a quarter in length and almost one-half inch in diameter. They are shiny black like patent leather and covered with approximately 40 white dots. The antennae are twice as long as the body and marked with alternating black and white bands. Adults are present from May to October.
Female beetles lay eggs in small holes chewed into the bark of a host tree. After an egg hatches, the tiny larva bores into the inner bark of the tree and begins to feed and grow. And grow. And grow. By the end of the summer the wrinkled white larva will be almost two inches long and will have tunneled deep into the heartwood of the tree. Tunneled branches and trunks are girdled and weakened and die quickly.
The larvae wait inside the tree until the following spring when they transform to the adult stage. Adults chew out through the bark creating piles of sawdust around large circular holes three-eighths to one-half inch in diameter. The new adults usually stay on the trees from which they emerged or they may disperse short distances and attack new trees, thus spreading the infestation.
Solutions
Currently the only effective means to eliminate Asian longhorned beetle is to remove infested trees and destroy them by chipping or burning. The number of trees cut down in five infested areas of New York since 1996 totals 4,346. More than 2,000 trees have been replanted, but a newly planted tree does not immediately take the place of the older established trees that were removed from the landscape. In Illinois, 1,243 trees have been destroyed in three areas of infestation. An energetic replanting program has put back more trees than were cut.
As drastic as these measures seem, they provide the best opportunity to eradicate the Asian longhorned beetle. Unchecked spread could create a nationwide problem worse than the Dutch elm disease.
Following discovery of Asian longhorned beetle in an area, thorough inspections are made to determine how far the beetle has spread. Areas of known infestation are then quarantined to prevent further accidental spread. Quarantine regulations prohibit movement of raw wood such as firewood, branches or stumps, and transport of any beetles.
You Can Help
Public awareness and cooperation will be essential to effectively contain and eliminate Asian longhorned beetle. If you travel to infested areas, please comply with the quarantine restrictions.
Also, help us look for possible infestations in other areas. Watch for the conspicuous spotted beetles during the summer. Be alert to possible signs of attack including large holes in tree trunks or branches and heavy accumulations of coarse sawdust.
If you discover beetles or suspect their damage, don't hesitate to contact your local county extension office, the Iowa State University Department of Entomology or the Iowa Department of Agriculture and Land Stewardship. Early detection is key to eradication. Let us help.
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