A photo taken June 20, 2025, shows dead and dying oaks near Whitewater Lake in Walworth County, following a period of defoliation and summer drought. / Photo Credit: Wisconsin DNR
By Bill McNee, DNR Forest Health Specialist
Bill.McNee@wisconsin.gov or 920-360-0942
Property owners are encouraged to monitor their trees for signs of decline and mortality, as the last few years have been marked by drought and spongy moth defoliation.
Landowners who have oak, birch, crabapple, aspen, willow, tamarack and basswood (linden) trees should be particularly watchful, because the caterpillars of this invasive insect prefer these species. Many other tree species are not preferred by the caterpillars and are less likely to be heavily defoliated, but are more likely to die if heavy defoliation should happen.
This article focuses on oak impacts.
The 2021-24 spongy moth outbreak has now collapsed statewide; no defoliation has been observed as of late July 2025. Only a few reports of single caterpillars were received by Wisconsin DNR Forest Health staff. (Note: Parts of Wisconsin may be experiencing a continuing outbreak of different caterpillars known as “oak leafroller” and “larch casebearer.”)
Continue reading “Monitor Your Trees For Spongy Moth-Related Decline And Mortality”
The Wisconsin Department of Natural Resources is partnering with the UW-Madison Division of Extension to host a series of fall workshops on invasive species plant identification and management. Learn about invasive plants in urban settings, focusing on identification, impacts, management and available resources. Dr. Mark Renz (professor and Extension specialist with UW-Madison) will lead the instruction, with Travis Wilson, Matt Wallrath and John Zabrosky assisting. Each workshop will include morning classroom instruction followed by hands-on field demonstrations in the afternoon. The cost of the workshop is $40 and includes lunch. 
Are you a forestry expert interested in working with the Wisconsin Department of Natural Resources (DNR), forest industry professionals and natural resource leaders to ensure sustainable management practices of Wisconsin’s forest resources?
Earth Day, Arbor Day and spring are all quickly approaching, and now is the time to start thinking about your tree plantings! Choosing the proper tree for a specific location will help ensure your tree’s long-term health and survival.
The Wisconsin Arborist Association (WAA) and the Wisconsin Department of Natural Resources (DNR)’s Urban Forestry program cohosted their annual conference on Feb. 16-18 in Green Bay. One of the preeminent events in arboriculture and urban forestry, the gathering brought together hundreds of people from the private, public, nonprofit and academic sectors to network and share knowledge about urban forest management.
This year was a record-breaker: 946 attendees, the highest mark ever. Data was also compiled regarding organizational affiliations of attendees this year.