Forest Health News

Aerial Spraying For Spongy Moth Planned at Perrot State Park

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A map showing the area to be covered by a 2026 aerial spray for spongy moth caterpillar control at Perrot State Park.

A map showing the 2026 spongy moth caterpillar aerial spraying area planned for Perrot State Park in Trempealeau County. / Map Credit: Wisconsin Department of Agriculture, Trade and Consumer Protection.

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

This spring, a portion of Perrot State Park in Trempealeau County will be aerially treated for spongy moth with “Foray” bacterial insecticide, containing Bacillus thuringiensis var. kurstaki.

A reproducing population of the leaf-eating caterpillar was detected in the park last fall, leading to the decision to conduct aerial spraying in 2026.

Continue reading “Aerial Spraying For Spongy Moth Planned at Perrot State Park” →

April Brings Celebration of Wisconsin’s Forests

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An overhead view of a group of children kneeling in a circle while planting a tree.

A group of children in Cedarburg gathers to plant a tree as part of an Arbor Day observance. / Photo Credit: Wisconsin DNR

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

It takes more than one celebration to pay tribute to Wisconsin’s 17 million acres of rich, diverse forestland.

So, the state has come up with multiple ways to acknowledge the value of trees to Wisconsin’s ecology, economy, health and way of life. Three of the biggest ones are taking place in April:

  • Earth Day will be observed on Wednesday, April 22.
  • Arbor Day is set for Friday, April 24.
  • Forest Appreciation Week runs April 20-24 statewide, covering both of those dates.

Continue reading “April Brings Celebration of Wisconsin’s Forests” →

Video Explains Importance Of Oak Wilt Prevention

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A frame-grab from the Wisconsin DNR's video explaining the tree disease oak wilt.

Landowner Montgomery Mouw and DNR Forest Health specialist Linda Williams inspect oaks as part of a DNR video explaining the disease oak wilt. / Photo Credit: Wisconsin DNR

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

Owners of oak trees, the time for caution is now.

Your oaks are at risk of oak wilt infection if they undergo pruning work or are damaged —even inadvertently — between April and mid-July.

Continue reading “Video Explains Importance Of Oak Wilt Prevention” →

‘Exploding Trees’ Face Long-term Impacts

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A long vertical wound in a tree trunk caused by deep freezing.

Cracked bark and wood creates a long vertical wound typical of the phenomenon commonly called “exploding trees.” / Photo Credit: Wisconsin DNR

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

This past winter, “exploding trees” went viral on social media. Many news outlets followed up with a more realistic explanation of the dramatically named phenomenon, pointing out that while the bitter cold can cause sudden cracks to form on trees, the trees don’t truly explode.

But what happens to those damaged trees as we warm up and move into the growing season?

Continue reading “‘Exploding Trees’ Face Long-term Impacts” →

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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Keep Invasive Plants Out Of Spring Planting Plans

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The invasive plant japanese barberry growing in a woodland area.

Originally planted as a garden ornamental, Japanese barberry can quickly escape cultivation and invade Wisconsin’s woodlands. / Photo Credit: Wisconsin DNR

By Wisconsin DNR

As winter begins to loosen its grip on Wisconsin, many gardeners have turned their thoughts to that unmistakable harbinger of spring: Planting season.

While dreaming of spring blooms and designing your next garden or landscape layout, consider that invasive plants may try to weed their way into your plans.

Continue reading “Keep Invasive Plants Out Of Spring Planting Plans” →

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.

Continue reading “Yard Tree Owners, Send In Your Questions” →