The 2018 gypsy moth trapping season has ended and results are in: 76,447 moths were caught in 10,748 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. In 2017, traps caught 108,808 moths.
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 catch only male gypsy moths because the females do not fly.
Trapping data helps determine potential sites for next year’s aerial spray treatments. About 76,288 acres across 14 counties were successfully treated this year. Treatment sites for next year have not yet been finalized.
“There were long periods of severe cold in northern and central Wisconsin this past winter, which, combined with treatments, contributed to the 29 percent decrease in gypsy moth catches we observed statewide,” said Michael Falk, trapping coordinator for the program. “Small population increases, however, occurred in isolated areas in the state.”
Severe winter cold can kill gypsy moth eggs, especially when coupled with a lack of insulating snow cover. This decreases the number of caterpillars that hatch from egg masses the following spring and drives population sizes down.
From now until next spring, people can help reduce the population of caterpillars next year 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 and tree mortality 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 then hatch the following spring, and the cycle begins again.