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State gypsy moth numbers higher in 2020

The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) caught 83,720 gypsy moths in 10,139 traps in Wisconsin this summer as part of the federal Slow the Spread of the Gypsy Moth Program.

“Weather conditions were relatively mild across Wisconsin compared to the previous two years,” said Michael Falk, DATCP’s gypsy moth trapping coordinator. “Winter temperatures were not low enough to kill gypsy moth eggs, and spring conditions did not support the fungal and viral diseases known to kill gypsy moth caterpillars. As a result, gypsy moth populations rebounded after two consecutive years of population decrease.”

Gypsy moth trapping is a tracking tool that measures the quantity and location of moth populations. Trapping data helps determine potential sites for next year’s aerial spray treatments. For 2020, DATCP treated about 145,625 acres in 18 counties. Treatment sites for next year will be available in March.

From now until next spring, anyone can help reduce the population of caterpillars by treating or removing gypsy moth egg masses. A gypsy moth egg mass is tan, oval, and about the size of a quarter. It has a velvety texture and can hold 500-1,000 eggs. You can find egg masses on trees, vehicles, fences, playground equipment, buildings, or any outdoor item. To remove an egg mass, use a putty knife, stiff brush, or similar hand tool and place the mass in warm, soapy water. Soak for a few days and then discard in the trash. You can also spray horticultural oil onto egg masses. Simply crushing an egg mass will not destroy it.

Gypsy moth is an invasive pest that has been spreading westward since its introduction to North America. In Wisconsin, gypsy moth is well established in the eastern two-thirds of the state. DATCP focuses its efforts on the western edge of that area in an attempt to slow the spread of this destructive insect. Gypsy moth caterpillars feed on the leaves of many species of trees and shrubs, especially oaks, and can cause severe leaf loss when feeding in large numbers.