By Bill McNee, Forest Health Specialist, Oshkosh
bill.mcnee@wisconsin.gov or 920-360-0942
Mature spongy moth caterpillar on a leaf. Photo: Bill McNee, Wisconsin DNR
Wisconsin Department of Natural Resources Forest Health staff are cautioning Wisconsin residents that the next two months could bring the worst spongy moth outbreak in more than a decade.
The caterpillars of this invasive insect prefer to feed on oak, birch, crabapple, aspen and willow leaves, but will also feed on many other tree and shrub species.
Southern Wisconsin and parts of the north are already in a high-population outbreak that is predicted to continue and spread. Populations have remained high due to a low incidence of caterpillar-killing diseases last summer. In addition, weather conditions in 2023 are favorable for the caterpillars and unfavorable for Entomophaga maimaiga, a fungus that kills spongy moth caterpillars.
Property owners are encouraged to examine their trees and take action. Specifically: