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Asian Longhorned Beetle

October 8, 2003

Asian longhorned beetle is in the news again, with a new infestation being found in the Toronto, Canada, area. This infestation appears to be limited to an area of about four square blocks in an industrial area of the city. In the Chicago area, eradication efforts are being successful, with two areas declared eradicated last fall. No infestations have been found so far this year. If that trend holds, two more areas will be declared eradicated at the end of 2003. This will leave only the Ravenswood area of Chicago. If no more infestations are found, it will be declared to be free of the beetle in 2008. Unfortunately, the New York City infestation continues to spread, so it does not appear that eradication of the beetle in North America is in the near future.

In the meantime, it is important to remain vigilant for signs of this insect. It attacks a variety of trees, including maple, box elder, poplar, plum, alder, birch, willow, horsechestnut, elm, ash, and hackberry. The adult beetle emerges through a hole that is perfectly round and 3/8 to 1/2 inch in diameter. The beetles are shiny black and about 1-1/4 inches long. They have long antennae banded in black and white, and the back of the beetle has about 40 white spots of various sizes.

After mating, the female chews a 1/4-inch-diameter hole with sloping sides through the bark, laying an egg in the cambium area. This type of hole is diagnostic for this pest, not being produced by any other insect in North America. The egg hatches into a larva that tunnels extensively through the cambium area before eventually tunneling deeper into the wood. Larvae are legless, white, and elongate, with a brown head area. Full-grown larvae approach 3 inches in length and create large tunnels through the wood. Infested trees show severe dieback of the canopy.

The larva pupates in the tunnel that it creates, with the adult chewing the large, round hole in the bark through which it emerges. Adult emergence is most common during June and July, but adults have been found from spring to December. The adult beetles can fly at least 0.6 mile but most commonly only fly to the next host tree, which may be a very short distance.

Funding and other support from the City of Chicago, Illinois Department of Agriculture, USDA–APHIS, and other federal agencies have allowed the quick removal of infested trees. Infested trees are chipped into pieces small enough to kill any larvae, pupae, and adults--and then burned, which kills all stages of this beetle. Removed trees have been replaced with support from the City of Chicago. Potential host trees outside the core-infestation areas were treated with Mauget-applied Imicide (imidacloprid) to kill egg-laying adults, larvae, and emerging adults.

Author: Phil Nixon


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