Statewide Forest Health

Fungicide For HRD Stump Treatment Available In Smaller Size

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A bag of Tim-bor Professional, a borate-based chemical that fights Heterobasidion root disease. / Photo Credit: Wisconsin DNR

By Kyoko Scanlon, Forest Pathologist, Fitchburg
Kyoko.Scanlon@wisconsin.gov

People who have been dealing with Heterobasidion Root Disease (HRD) may be familiar with the product name “Cellu-Treat®.” It has been used to treat fresh cut stumps to prevent HRD.

But Cellu-Treat® is not the only chemical available for HRD. Another borate-based chemical, Tim-bor® Professional, can also be used legally for the same purpose in Wisconsin. Both products are manufactured by Nisus Corporation, and their labels are almost identical (Cellu-Treat label, Tim-bor label).

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Cooperative Hemlock Woolly Adelgid Trapping Effort Begins

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A 3-D printed trap used to collect hemlock woolly adelgid DNA. / Photo Credit: Wisconsin DNR

By Michael Hillstrom, DNR Invasive Forest Pest Coordinator, Fitchburg
Michael.Hillstrom@wisconsin.gov or 608-513-7690

This spring, the Wisconsin Department of Natural Resources (DNR) is collaborating with the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) to set traps to detect the invasive insect hemlock woolly adelgid (Adelges tsugae; HWA).

The project, funded by the Wisconsin Specialty Crop Block Grant Program, calls for traps to be set to detect the invasive insect. No detection of HWA has been made to date in Wisconsin forests. Continue reading “Cooperative Hemlock Woolly Adelgid Trapping Effort Begins” →

Species Spotlight: Japanese Honeysuckle

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Japanese honeysuckle climbing up nearby trees. / Photo Credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

By Carter Hellenbrand, DNR Invasive Plant Field Specialist, Fitchburg
Carter.Hellenbrand@Wisconsin.gov  

Note: This is the first installment in the Forest Health News “Invasives Spotlight” series, a monthly series of Forest Health News articles.

Many people recognize honeysuckle as a fast-spreading invasive shrub that can quickly displace native vegetation. But did you know that some honeysuckles exist as a vine?

Japanese honeysuckle (Lonicera japonica) is an invasive perennial vine that can grow to a length of 80 feet or longer. Birds will often eat and disperse the berries the vine produces, allowing for the creation of new populations.

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Campers Reminded: Don’t Move Firewood

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A self-service firewood point of sale at Mirror Lake State Park in Sauk County. / Photo Credit: Wisconsin DNR

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

With camping season about to enter full swing, the Wisconsin Department of Natural Resources (DNR) urges campers to think twice before giving invasive species or harmful hitchhikers a ride in their firewood.

Memorial Day marks the unofficial start of summer, and campfires are a Wisconsin summer staple. And campers should know it’s a big help to the state’s trees when they help to prevent the spread of invasive pests by making smart firewood choices.

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Huge White Grubs Found In Firewood, Rotting Logs

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Closeup of large white grub larvae discovered inside logs being split for firewood.

Large white grub larvae discovered while splitting firewood. The insects are living in a piece of firewood with a lot of decay. / Photo Credit: Wisconsin DNR

By Linda Williams, DNR Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov or 920-360-0665

Hermit flower beetles (Osmoderma spp.) are very large scarab beetles, sometimes called leather beetles.

Three Osmoderma species can be found in Wisconsin, though none are common. Adult beetles look big and beefy but are harmless, eating a little pollen, feeding on ripe fruit and sipping nectar and tree sap during their adult life.

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Salt Spray Damage Impacts White Pine

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A closeup of white pine needles showing browning due to damage from roadside salt spraying.

White pine with browning needles and needle tips from roadside salt spray damage. The uninjured overwintering buds at the base of the shoot will produce a new flush of growth in the spring, thereby reducing the visual appearance and health impact of the damage. / Photo Credit: Wisconsin DNR

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

An active winter weather season for snow, freezing rain and fluctuating freeze/thaw temperatures has exposed white pine along roadways to salt spray damage.

Vaporized salt spray droplets from vehicle traffic can drift into the air and settle onto vegetation, with the heaviest deposits occurring within 150 feet of a roadway.

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Jumping Worms A Threat To Gardens And Forests

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Closeup of a jumping worm on soil.

Closeup of a jumping worm (Amynthas agrestis). / Photo Credit: Wisconsin DNR

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

Invasive jumping worms are worrisome for several reasons, but here’s one of the main ones: It can be difficult to tell you even have them until they’ve already done their damage.

That makes this time of year important, because the best way to avoid damage from jumping worms, which can be substantial and long-lasting, is to prevent them from getting into your garden, yard or forestland in the first place.

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Yard Tree Owners, Send In Your Questions

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The niversity of Wisconsin-Madison Division of Extension Horticulture Program's webpage for "Ask A Gardening Question."

The University of Wisconsin-Madison Division of Extension Horticulture Program’s webpage for “Ask A Gardening Question,” the best place for homeowners to ask questions about the health of their yard trees. / Graphic Credit: UW-Madison Division of Extension

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

The Wisconsin Department of Natural Resources (DNR) has a team of Forest Health specialists that focus on problems affecting state, county and municipal forests and private forests larger than 10 acres.

But, to twist a cliché, if you can’t see the forest for the trees when it comes to your yard trees, expert help is a few clicks away.

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Oak Wilt Information Updated

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University of Wisconsin-Madison Extension online tool to help with oak wilt decisions.

A University of Wisconsin-Madison Extension online tool provides users localized information about the estimated emergence status of the two most important insects that transmit oak wilt in Wisconsin. / Graphic Credit: University of Wisconsin-Madison Extension

By Kyoko Scanlon, DNR Forest Pathologist, Fitchburg
Kyoko.Scanlon@wisconsin.gov

In 2025, oak wilt was detected for the first time in Hughes Township, Bayfield County, a northern Wisconsin location where oak wilt remains uncommon. There were no new county finds in 2025.

Based on the findings in 2025, the maps in the Oak Harvesting Guidelines To Reduce The Risk Of Introduction And Spread Of Oak Wilt (the oak wilt guidelines), oak wilt fact sheet and were updated. The maps in the oak wilt guidelines are good through the end of 2026.

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Stilt Grass StoryMap Updated For 2026

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Main page of the Wisconsin DNR's StoryMap on Japanese stilt grass.

The main page of the Wisconsin Department of Natural Resources’ StoryMap titled “Japanese Stilt Grass on the Coulee Experimental State Forest.” / Graphic Credit: Wisconsin DNR

By Carter Hellenbrand, DNR Invasive Plant Field Specialist, Fitchburg
Carter.Hellenbrand@wisconsin.gov

The Wisconsin Department of Natural Resources (DNR) Forest Health program has updated the Japanese stilt grass StoryMap to reflect all the work completed in 2025. The StoryMap documents the history of this invasive species on the Coulee Experimental State Forest in La Crosse County.

A StoryMap is a web-based content creation and communication tool that allows creators to share maps, apps and multimedia in the context of a narrative. Users can see an overview of Japanese stilt grass, how to identify it and what control efforts have been implemented since the plant was first detected in Wisconsin in 2020.

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