Perfect time to find and treat gypsy moth egg masses
MADISON – As trees lose their leaves, exposing trunks and branches, state forestry officials say this is the perfect opportunity for property owners in Wisconsin to search for signs of gypsy moth infestation and take action against it.
Property owners should look for small, teardrop-shaped egg masses left behind by the moth stage of the leaf-eating caterpillar, according Mark Guthmiller, a regional gypsy moth suppression coordinator for the Wisconsin Department of Natural Resources.
The egg masses are the size of a nickel or quarter, tan-colored and covered with thousands of tiny, fuzzy hairs. They are firm to the touch and contain up to 1,000 individual gypsy moth eggs that will hatch next April or May. Old egg masses that hatched last spring are soft, pale and not a concern. Egg masses can be found on tree trunks and the underside of branches, as well as on buildings, firewood, vehicles, play sets, and other outdoor objects. Pictures are online at: gypsymoth.wi.gov (exit DNR).
Guthmiller said egg masses within reach can be treated with tree-friendly horticultural oils that are labeled for gypsy moth egg masses and available at many garden centers.
“The best time to oil egg masses is anytime after the first few hard frosts in fall through the first week in April, when there is no danger of freezing temperatures,” he said. “Oiling egg masses is one of the best tools we have for reducing gypsy moth populations and helping to protect our yard trees from defoliation by gypsy moth caterpillars next summer.”
These oils are specially formulated and penetrate into the gypsy moth egg masses, suffocating the developing eggs inside so that they do not hatch next spring. Do not use motor oil or lubricant oils to treat egg masses because these can harm your tree. For instructions, visit: gypsymoth.wi.gov (exit DNR) and click on “management options for yard trees.”
People can also scrape the egg masses off of the tree and into a bucket of soapy water with a paint scraper or other sturdy tool. Let the egg masses soak for several days and then dispose of them in the trash.
“This is an easy option for people who find a few egg masses on the side of the house or on trees with smooth bark,” said Bill McNee, another regional gypsy moth suppression coordinator for the DNR. “When scraping egg masses off, do not let it break up and fall on the ground because the eggs will still hatch next spring. Masses that are hard to scrape off are best treated by oiling.”
If there are many egg masses, oil or remove those within reach and consider applying physical controls such as sticky barriers and burlap bands next spring when the caterpillars are present. Insecticide treatments may also be appropriate to control caterpillars. Many arborists in Wisconsin offer egg mass treatment and insecticide application services. For more information about gypsy moth control measures, visit gypsymoth.wi.gov (exit DNR), email dnrfrgypsymoth@wisconson.gov, or call 1-800-642-MOTH (6684) for help.
FOR ADDITIONAL INFORMATION: Bill McNee (Green Bay): 920-662-5430; Mark Guthmiller (Madison): 608-275-3223.
