Oil or remove gypsy moth egg masses now

Gypsy moth egg masses are tan colored lumps about the size of a nickel or a quarter. They are usually found on trees but may also be found on outdoor articles such as firewood piles, bird houses and picnic tables.

Gypsy moth egg masses.

Homeowners who are interested in reducing gypsy moth caterpillar numbers this summer should consider oiling or removing reachable egg masses well before the eggs begin hatching in the second half of April. Gypsy moth egg masses are tan-colored lumps about the size of a nickel or quarter, and usually contain 500 to 1,000 eggs. The egg masses can be found on any rough or protected surface including trees, houses, firewood piles, bird houses and other outdoor objects. Do NOT scrape the egg masses onto the ground or step on them or break them apart. Many of the eggs will survive and still hatch.

Horticultural oils that suffocate the eggs are available at many garden centers and large retailers. In general, these are applied when temperatures are above 40oF and freezing is not imminent. If removing egg masses, scrape them into a can of soapy water and then let them soak for a few days before discarding in the trash.  More information about management options for homeowners and woodlot owners is available online. 

Property owners looking to hire a business to do insecticide treatments this spring should contact them soon. The Wisconsin Arborist Association has a list of certified arborists. Additional businesses offering insecticide treatments may be found in the phone book under ‘tree service.’ Homeowners can also purchase insecticides at garden centers and large retailers.

Written by: Bill McNee, forest health specialist, Plymouth (Bill.Mcnee@Wisconsin.gov), 920-360-0942.