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The City of Madison Streets Division’s Urban Forestry Department is asking residents to help control the gypsy moth population.

This winter please look for and then destroy the egg masses for this species that are on your property.

Why do this?
The moths (Lymantria dispar) are a destructive pest. They can defoliate and weaken trees.

While the moths prefer oak trees, all tree species can be harmed.

The egg masses from the moths can now be found on trees and other surfaces. These masses can hold  500 to 1,000 eggs.

And, according to the Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP), the population of this species has increased over the past two years.

By destroying the egg masses, you help control this damaging pest and help keep our urban forest healthy.

How do I help?
First, be sure what you see are in fact are moth egg masses. They are a fuzzy, brownish patch typically found on tree trunks, but can also be found on sheds, under picnic benches, and most other flat surfaces.

Next, choose one of the eradication methods:

  • Golden Pest Oil

Apply a product called golden pest oil to the eggs. This is a natural soybean oil that can be found at garden centers. The oil prevents the eggs from hatching.

If you elect this method, please use the oil as directed.

  • Scrape & Submerge

Use a putty knife or similar flat edged scraping tool, remove the egg mass and submerge it within a container of soapy water. (You can use household dish soap.) Keep the eggs submerged for two days before discarding them into the trash.

Can you just stomp on them after they are removed from the tree?
DATCP does not recommend this method. Egg masses are hardy and have evolved to withstand extreme conditions, and would likely survive simply just stepping on them.

The best option would be to use the soapy water or golden pest oil application described above so the eggs do not hatch.

What about aerial spraying?
This is a program that was discontinued for Dane County. DATCP continues supporting spring and summer aerial spraying in certain counties in western Wisconsin. Additional details about the spraying effort can be found on their webpage.

What if I find an egg mass on a tree that’s on public property?
Contact the Urban Forestry Department at 608-266-4816 to let them know what you have seen.

Additional Information
More details regarding the moth and management practices can be found on the State of Wisconsin’s website.

More information regarding homeowners managing this pest on their property can be found on the University of Wisconsin’s Extension page.

About the Name
The Entomological Society of North America is in the process of selecting a new name for this species. Since a new name has yet to be established, this release uses the one still in current use. We acknowledge the species name contains a pejorative term for the Romani people, and tried to use it sparingly. We look forward to utilizing the new name and updating the Urban Forestry information once the Entomological Society of North America reveals their choice.