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Wandering Gypsy Moths Get Nasty Surprise

By Jan Suszkiw
April 13, 1999

A homeowner’s springtime battle against gypsy moths often comes down to placing burlap skirts around tree trunks, where young caterpillars can be easily removed.

But Geoffrey White sees room for improvement. The Agricultural Research Service entomologist has found that applying a latex coating of chlorpyrifos insecticide beneath the skirts can kill more than 60 percent of the pests. He works at the Insect Biocontrol Laboratory, operated in Beltsville, by ARS, the U.S. Department of Agriculture’s chief scientific agency.

The burlap skirt is among the few first-line defenses available to home or property owners against the moth, Lymantria dispar, whose caterpillars devour the leaves of hundreds of trees species, oak being a favorite.

Combining the skirts and coating exploits the pests’ natural tendency to seek daytime shelter before emerging at dusk to feed high in the tree’s canopy. Property owners must ambush the pests well before then. Usually, dropping them in a bucket of soapy water or bleach does the trick. But on large properties this can become tedious and messy.

To save time and ensure fewer caterpillars escape notice, White’s approach calls for brushing the latex coating directly onto the bark beneath the skirts. That way, instead of refuge, the pests get a small but lethal dose of insecticide. In a 31-day experiment conducted last summer, a single, six-hour exposure killed 64 percent of caterpillars hiding beneath the skirts. On untreated, skirted trees, 95 percent survived.

White hopes to replicate the results this spring. If follow-up studies are successful, he may explore substituting chlorpyrifos with a biopesticide containing beneficial fungi that kill by growing inside the moth. A longer story appears in Agricultural Research magazine’s April issue on the web at:


Scientific contact: Geoffrey White, ARS Insect Biocontrol Laboratory, Beltsville, Md., phone (301) 504-5869, fax (301) 504-8190,