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Asian Longhorned Beetle

July 22, 1998

Asian longhorned beetle, Anoplophora glabripennis, has been discovered in a small area of Chicago, in a six-square-block region in the Ravenswood area. This insect is native to China, Korea, and Japan. The latitude of its distribution in the Far East corresponds in North America as running from Cancun, Mexico, to Milwaukee, Wisconsin. The only other place it has been found on North American trees is in Amityville and Brooklyn, New York, both on Long Island, where it was found in August 1996.

Asian longhorned beetle tunnels not only into dead and dying trees but also attacks apparently healthy trees. It prefers maple, poplar, and willow but will attack horsechestnut, mulberry, plum, pear, black locust, elm, Chinaberry, citrus, birch, and rose of Sharon. Among the maples, Norway, sugar, silver, and sycamore are the most common hosts.

Adult Asian longhorned beetles are shiny black and approximately one inch long with about 40 irregular-sized and -shaped white dots on the wing covers. They have black-and-white-banded antennae that are at least as long as the body. Adults are present from August through October in China, peaking in July. They have been reported as early as mid-May by New York residents.

Adult beetles feed on the bark of twigs and small branches after emerging. They may migrate as much as 6/10 of a mile in search of host trees. Females chew 3/8-inch diameter pits through the bark and then lay an egg in each pit. Individual adults live for several weeks, with each female laying 25 to 32 eggs.

The hatching larvae tunnel just under the bark in the cambium. Older larvae tunnel deep into the tree at an upwards angle; larval tunnels are four to six inches long. Larvae push frass consisting of wood fibers and feces out of the tunnels. The larvae spend the winter deep in the tree, tunneling and feeding again in the spring before pupating in late spring or summer in the larval tunnel. Adults emerge from the tree through 1/4- to 1/2-inch round holes. Most life cycles last one year, although some last for two years.

Damage consists mainly of weakened branches that break off during heavy winds. Attack for several years could cause the death of branches, limbs, or entire trees. Although many insect borers and the yellow-bellied sapsucker make 1/4-inch diameter holes in trees, emergence holes approaching 1/2 inch are uncommon. Cottonwood borer makes this size of hole in cottonwood and other poplars, but that pest is uncommon in Illinois. Carpenter bees make holes this big but normally attack lumber or the cut end of logs. The shallow egg-laying holes made by Asian longhorned beetle females are similar to those made by woodpeckers searching for insect larvae in or under the bark. However, these beetles make round holes that are similar in diameter, whereas woodpeckers tend to make jagged holes of various sizes.

Control is difficult due to the extended adult emergence period. Insecticide treatment would require several applications, which is not practical and may not be very effective. This beetle is eliminated by cutting down all infested trees and chipping or burning them. Areas where the beetle is found are placed under quarantine to prohibit movement of host species firewood, logs, green lumber, stumps, roots, branches, and debris of 1/2 inch or more in thickness out of the area.

Beetles or wood with suspected beetle damage should be submitted to the Plant Clinic, 1401 St. Mary’s Road, Urbana, IL 61802 or to your local Extension office for forwarding to the Plant Clinic for positive identification.

Author: Phil Nixon


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