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Increased Tree Mortality Seen As Spongy Moth Outbreak Ends

Mature spongy moth larva on a tree at Potawatomi State Park in Door County, July 2025.

Mature spongy moth larva on a tree at Potawatomi State Park in Door County, July 2025. / Photo Credit: Wisconsin DNR

By Bill McNee, DNR Forest Health Specialist, Oshkosh
Bill.McNee@wisconsin.gov  

Wisconsin’s recent period of high spongy moth populations (an “outbreak”) came to an end in 2025, as the remaining known hotspots were aerially sprayed or naturally collapsed. Only a handful of large larvae were observed or reported by property owners.

Spongy moth populations are likely to be low across the state for at least the next few years. However, it is possible that some sites may experience a population increase before then, if local weather conditions are favorable for the insect.

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Stumping Heterobasidion Root Disease With Cellu-Treat®

Photo of a freshly cut tree stump after treatment with fungicide to prevent infection with Heterobasidion root disease. The fungicide is dyed blue to help ensure complete coverage.

A freshly cut tree stump after treatment with fungicide to prevent infection with Heterobasidion root disease. The fungicide is dyed blue to help ensure complete coverage. / Photo Credit: Wisconsin DNR

By Tim Shively, DNR Forest Health Specialist, Eau Claire
Timothy.Shively@wisconsin.gov or 608-772-6974

Treating freshly cut conifer stumps is critical to preventing infection by Heterobasidion species, causal agents of Heterobasidion root disease (HRD).

Within this genus, H. irregulare is believed to be the only species in Wisconsin, and it causes the mortality of overstory pine and spruce trees. The DNR has developed comprehensive guidelines to assist landowners, property managers, foresters, and loggers with determining whether stump treatments are necessary to prevent the introduction or spread of HRD at a given site.

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Tree Inventory Subaccounts Available Within Wisconsin Community Tree Map

By Dan Buckler, DNR Urban Forest Assessment Specialist; Daniel.Buckler@wisconsin.gov or 608-445-4578

Do you have a tree inventory but have a hard time keeping it up to date? Or are you interested in inventorying trees from scratch?

The Department of Natural Resources (DNR) has made a handful of “subaccounts” available for communities or organizations to edit data within the Wisconsin Community Tree Map at no cost to the community or organization.

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American Forests Launches Tree Equity Coaching Network

American Forests LogoThe  American Forests National Coaching Network is a community for urban foresters, community advocates, city leaders and allied professionals to connect, learn, inspire and cultivate city commitments to advance tree equity. This network is a way for people to address challenges and build their tools and resources. Continue reading “American Forests Launches Tree Equity Coaching Network”

Programs Support Forestry, Forest Products Industry

United States Department of Agriculture logo.

Elle Soderberg, DNR Forest Products Specialist, Green Bay
Elle.Soderberg@wisconsin.gov

Communities across Wisconsin have significant economic growth opportunities thanks to several key funding and support programs offered by Rural Development, a division of the U.S. Department of Agriculture (USDA). These programs provide vital resources aimed at improving infrastructure, businesses and entrepreneurs across the country.

The Business & Industry Loan Guarantees program is designed to assist businesses in rural areas by offering loans that help promote economic development, job creation and improved services in communities that need it most. Through this initiative, businesses can access funding they may not have otherwise qualified for, thus enhancing their ability to expand and create new opportunities for local residents.

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Right Tree, Right Place

By Olivia Witthun, DNR Urban Forestry Coordinator
Olivia.Witthun@wisconsin.gov or 414-750-8744

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.

Think: “Right tree, right place.” It’s an old phrase, but the message is powerful and remains true today.

When selecting the right tree for your spot, many factors must be considered. Check out Choosing the Right Landscape Plants: Factors to Consider for a list of important considerations, such as landscape function, size and form, ornamental factors and pest issues. It even includes information on how to select high-quality trees in the nursery. Continue reading “Right Tree, Right Place”

New Tree Canopy Resources Released

By Dan Buckler, DNR Urban Forest Assessment Specialist
Daniel.Buckler@wisconsin.gov or 608-445-4578

Urban Tree Canopy (UTC) assessments using aerial or satellite imagery have been one of the primary ways people estimate the extent of urban forests across an area of interest, whether it be a single park, a streetscape or a whole community.

Two recently released UTC resources are ready for use by Wisconsin communities and urban forestry practitioners. The first, TreeCanopy.us, is a mapping application that shows UTC and other land cover in urban areas across the country for 2017 and 2022. It also shows changes in canopy cover between those five years. Continue reading “New Tree Canopy Resources Released”

Make Plans Now To Fight Spongy Moth In 2025

A photo showing large egg masses on a tree at the Kettle Moraine State Forest-Southern Unit in 2021.

Large egg masses are seen on a tree at the Kettle Moraine State Forest-Southern Unit in 2021. / Photo Credit: Bill McNee, Wisconsin DNR

By Bill McNee, DNR Forest Health Specialist, Oshkosh
Bill.McNee@wisconsin.gov or 920-360-0942

Part Two of a report on spongy moth in Wisconsin in 2024 and 2025. Part One was published in December.

The Wisconsin Department of Natural Resources (DNR) is encouraging property owners to examine their property for spongy moth egg masses and plan for action this spring if needed. Each spongy moth egg mass contains hundreds of eggs that will hatch into hungry, leaf-eating caterpillars this spring. Large numbers of these invasive caterpillars can be a tremendous nuisance that may cause tree mortality.

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Tree Disease Maps Have Migrated

The Wisconsin web map for Heterobasidion root disease, available through ArcGIS Online.

The Wisconsin web map for Heterobasidion root disease, available through ArcGIS Online. / Map Credit: Paul Cigan, Wisconsin DNR

By Paul Cigan, DNR Forest Health Specialist, Hayward
Paul.Cigan@wisconsin.gov or 715-416-4920

The Wisconsin Department of Natural Resources (DNR) Forest Health program hosts two interactive web maps on its webpage:

Heterobasidion Root Disease

Oak Wilt Seasonal Harvesting Opportunities

Continue reading “Tree Disease Maps Have Migrated”

DNR Recruiting For Two Forest Health Specialists

A Wisconsin map showing zones of coverage for each of the six DNR Forest Health Specialists

A map showing the zones of coverage for each of the six DNR Forest Health Specialists. / Graphic Credit: Wisconsin DNR

By Art Kabelowsky, DNR Outreach and Communications;
Arthur.Kabelowsky@wisconsin.gov or 608-335-0167

The Wisconsin Department of Natural Resources (DNR) has opened the search for candidates to fill two Forest Health Specialist openings, one in the West Central zone and one in the South Central zone.

The posting can be seen on the WiscJobs website. To be considered, candidates have until the posted deadline of 11:59 p.m. Monday, Jan. 6, 2025, to submit a resume and letter of qualifications.

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