Spongy Moth (Lymantria dispar)
The City of Madison Urban Forestry Section has received reports of spongy months at all life stages at several locations in the city.
Management of this pest are up to local units and residents.
resources for homeowners
If you have concerns about spongy moths on trees on your private property, residents should use these resources.
The State of Wisconsin has a spongy moth portal with links to provide guidance on how to identify these insects and their egg masses, how to predict the damage the moth's can cause, among other resources.
The University of Wisconsin Extension has a management guide for homeowners outlining some of the steps you can perform.
You can also contact a certified arborist for help.
how to destroy egg masses
To help control the moth population, residents can destroy the egg masses. The best time to do this is during the winter up until spring. Masses look like fuzzy brownish patches that can be found on tree trunks, under picnic tables, along sheds, and many other flat surfaces.
Egg masses can hold up to 1,000 eggs, so destroying them on your property can help control this pest.
Here are the two methods that are most effective at destroying the egg mass:
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.
what to do if you see signs of the spongy moth of city-owned trees on the terrace?
Contact us and we will take the next appropriate steps.
what about aerial spraying?
In past years, the Wisconsin Department of Natural Resources (DNR) had offered communities the option to pay for a state-arranged aerial spray program for both public and private property for this pest as part of a suppression program. This suppression program did not eliminate the pest all together but it reduced the population and the effect it has on trees. The DNR has ended this program in places where the moth is established (like in Madison).
A different state agency, the Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP) has a separate spraying program, but it focuses solely on counties near the Iowa and Minnesota border to help slow the spread of the moth into those states.
why are spongy moths a problem?
Spongy moth feeding leads to summer defoliation of our trees.
And the caterpillars can cause an itchy rash in some people.
new name for same species
Spongy moth is the new name for the species once known as the "gypsy moth." The old name contains a racial slur for the Romani people, and the new name was decided by the Entomological Society of America as part of their Better Common Names Project.