The 2010 gypsy moth trapping season in Wisconsin has ended, and the number is in: 142,409 moths caught statewide. The majority of the 28,150 traps were set in western Wisconsin this summer as part of the Wisconsin Department of Agriculture, Trade and Consumer Protection "Gypsy Moth Slow the Spread Program."
Trapping for gypsy moths is not used as a method of population control; it is a measuring tool. It shows where the moths are located and the extent of its 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 221,313 acres were treated in 20 counties this year. Treatment sites for next year have not been finalized.
In 2009, traps caught 132,275 moths. Though there is no definitive explanation to this year's minor increase in moth catches, there are possible explanations.
"Spring was mild and dry this year, favorable conditions for gypsy moth development," Gypsy Moth Trapping Coordinator Chris Whitney said. "Other reasons may also include better trapping lures, the natural progression of the moth's movement westward and larval drift. A high instance of female larvae mortality may also be a cause, and with the lack of female moths, this may force male moths to fly longer distances in search for a mate."
Counts of moth catches may even have been higher had there not have been some help. 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.
From now until spring, people can help decrease the number of next year's caterpillars by treating or removing egg masses. A gypsy moth egg mass is tan, oval or tear-shaped and a little bigger than a quarter. It is flat and has a velvety texture. Egg masses can be found on trees, vehicles, fences, playground equipment, buildings and any outdoor item. An egg mass can hold 500 to 1,000 eggs.
Egg masses can be scraped off with a putty knife, stiff brush or similar hand tool and dropped 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. Crushing the egg masses will not destroy the eggs.
The gypsy moth is an invasive pest from Europe and Asia that has been spreading westward since its introduction to North America in 1869. Gypsy moth caterpillars feed on many species of trees and shrubs, especially oaks, and can cause defoliation when feeding in large numbers. As moths, the males concentrate on finding a female to mate. Females lay an egg mass, and the moths die. Caterpillars then hatch the following spring, and the cycle starts again.