Sign up now for spray suppression program

Look for egg masses in crevices and protected hiding spots on rough bark, the undersides of branches, under signs attached to trees, and even on buildings, play equipment, benches, and picnic tables.

You can predict whether spongy moth (Lymantria dispar) caterpillars are likely to defoliate your trees next June. This is best done once leaves have fallen. Directions on how to perform a predictive survey are available online at www.gypsymoth.wi.gov.

If you want to participate in the suppression spray next spring, contact your county suppression coordinator now.

When the temperature is above 40°F, spray egg masses with a dormant horticultural oil (such as Golden Pest Spray Oil) to kill them and reduce the population of spongy moth next spring.   The spray oil kills the eggs, reducing the population of spongy moth next spring.  This spray oil is available to purchase online or at some garden centers and retailers.  If you have many egg masses, consider adding food coloring to your spray oil so you can see which egg masses you’ve already treated.  Although more difficult, and you must be careful not to damage the bark of the tree, you can also scrape egg masses into a container and cover them with soapy water for 2 days.  You may then discard eggs in the trash. Don’t leave any part of the egg mass attached and don’t allow it to fall onto the ground, they will survive to hatch next spring!

Spongy moth egg masses hidden on the underside of a picnic table
Spongy moth egg masses on the underside of branches
Photo Credits:  Mark Guthmiller, WI DNR