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April 5, 2011

EDITORS' NOTE: This is the first of several articles that will be submitted between now and July regarding gypsy moth in Wisconsin. Each article will highlight a different strategy for managing gypsy moth populations. All of these strategies are effective and some readers may find one more useful than the rest for their situation. Please consider sharing information from all of these releases with your audiences .

MADISON - As spring approaches, state forestry officials are urging homeowners to look for signs of gypsy moths. Beginning in late April, a new generation of gypsy moth caterpillars will hatch in Wisconsin.

"At high numbers, gypsy moth caterpillars are a tremendous nuisance. They strip trees of their leaves, which may kill the tree," says Bill McNee, a gypsy moth suppression coordinator with the Department of Natural Resources in Oshkosh. "The insect's favorite food is oak leaves, but it will feed on many other tree species such as birch, crabapple, aspen and willow," said McNee.

Wet weather last year helped kill many caterpillars before they had a chance to lay egg masses, which means fewer will be hatching this spring. However, gypsy moth populations are still at damaging levels in parts of northeast, southeast, and south central Wisconsin. In response to the threat, eight counties will participate in a state-organized aerial spray program this spring. Final maps of the areas that will be sprayed by planes this May are available at the state gypsy moth web site [] (exit DNR).

With or without aerial spray treatments, homeowners are urged to take action to reduce the number of caterpillars that will hatch and feed on their trees.

gypsy moth egg mass
Gypsy moth egg mass

"As soon as possible in April, search for the tan-colored egg masses and destroy any within reach," McNee says. Egg masses are about the size of a nickel or a quarter.

The egg masses can be found on any protected surface including trees, houses, firewood piles, bird houses, and other outdoor objects. Before mid-April, oil the egg masses with a horticultural oil labeled for gypsy moth, such as Golden Pest Spray Oil. DO NOT use products such as motor oil or axle grease because they can harm the tree. If property owners prefer, they can scrape the masses into a can and drown them in soapy water for at least two days to kill the eggs.

"Do NOT simply scrape the egg masses onto the ground, step on them, or break them apart. Many of the eggs will still survive and hatch," McNee cautions. "You will have 500 to 1,000 fewer caterpillars for every egg mass you properly oil before mid-April or drown before hatch."

After oiling or removing all of the egg masses within reach, people can place sticky barrier bands on trees. A demonstration of the technique is available on the University of Wisconsin-Extension website at: [] (exit DNR).

"These bands will prevent crawling caterpillars from climbing into your trees," says Mark Guthmiller, DNR gypsy moth suppression coordinator in Madison. At a convenient height, wrap a belt of duct tape 4-6 inches wide around each tree trunk, shiny side out. Smear the center of the band with a sticky, horticultural pest barrier available at garden centers. "Routinely sweep the caterpillars from the base of the tree into a bucket of soapy water to kill them," says Guthmiller.

People who have many egg masses on their property and are not in an aerial spray area can also hire a certified arborist to protect yard trees after gypsy moth caterpillars hatch. Insecticide treatments are most effective when done in May and early June.

"Spray while the caterpillars are small so they don't become a nuisance or strip the tree's leaves," McNee says. "Arborists are busy in the spring, so determine whether this is an option for you and then make arrangements soon."

People can find certified arborists by searching the Wisconsin Arborist Association Web site at [] (exit DNR). Also look in the phone book under 'Tree Service'.

More information on the gypsy moth's life stages and control options for yard trees and woodlots is available on the state gypsy moth web site [] (exit DNR).

FOR MORE INFORMATION CONTACT: Bill McNee, DNR Gypsy Moth Suppression Coordinator, northeast and southeast Wisconsin, (920)662-5430; Mark Guthmiller, DNR Gypsy Moth Suppression Coordinator, south-central Wisconsin, (608) 275-3223; Colleen Robinson Klug, Suppression Program Public Information Officer, statewide, (608) 266-2172.

Last Revised: Tuesday, April 05, 2011

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