Gypsy moth trap count decreased this year

Wisconsin State Farmer


From late June to late July, yellow planes contracted by the U.S. Forest Service in a joint project with the Wisconsin Department of Agriculture, Trade and Consumer Protection will be applying an organic, biodegradable mating disruptor to 19 sites in 9 counties in the western third of the state.

—The 2016 gypsy moth survey trapping season has ended and results are in: 86,462 moths were caught in 11,383 traps set in Wisconsin this summer as part of the Wisconsin Department of Agriculture, Trade and Consumer Protection’s Gypsy Moth Slow the Spread (STS) program.

Trapping for gypsy moths is not used as a method of population control; it is a tracking and measuring tool. It shows where the moths are located and the extent of the population. Traps only catch male gypsy moths because the females do not fly.

Trapping data helps determine potential sites for next year’s aerial spray treatments. Approximately 201,664 acres were successfully treated across 21 counties this year. Treatment sites for next year have not yet been finalized.

Areas selected for treatment during the summer have seen a decline in moth populations after the trapping data was collected. In 2015, traps caught 97,505 moths.

“There were some late spring freezes in some parts of the state, but I think a main reason, apart from treatments, would be the heavy rain that hit nearly every part of the state this summer,” said Chris Whitney, trapping coordinator for the program.  “There was an 11 percent decrease in the moth captures, however, moth populations can return quickly given the right conditions.”

The wet and rainy weather conditions in late spring and early summer induced the effects of the gypsy moth nucleopolyhedrosis virus and a fungus, Entomophaga maimaiga, causing widespread caterpillar mortality. The naturally occurring virus and fungus are less effective in drier conditions.

From now until next spring, people can help decrease the number of next year’s caterpillars by treating or removing egg masses. They can be found on trees, vehicles, fences, playground equipment, buildings, or any outdoor item. A gypsy moth egg mass is tan, oval or bulb-shaped, and a little bigger than a quarter. It is flat with a velvety texture and can hold 500 to 1,000 eggs.

Egg masses can be removed with a putty knife, stiff brush or similar hand tool and placed into a container of warm, soapy water. Let them soak for a couple of days and discard them in the trash. Horticultural oil also can be sprayed onto egg masses. Simply crushing the egg masses will not destroy them.

The gypsy moth is an invasive pest from Europe that has been spreading westward since its introduction to North America in 1869. Gypsy moth caterpillars feed on the leaves of many species of trees and shrubs, especially oaks, and can cause severe defoliation when feeding in large numbers. As adult moths, the males concentrate on finding a female to mate. Females lay an egg mass, and then the moths die. Caterpillars hatch the following spring, and the cycle begins again.

For more information, call the toll-free number 1-800-642-6684, e-mail or visit the website,