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Spongy Moth Population In Decline

Posted on by akabelowsky
A photo of a tree trunk showing spongy moth caterpillars killed by nucleopolyhedrosis virus (NPV) hang in an inverted “V” orientation; caterpillars killed by the fungus Entomophaga maimaiga hang vertically.

Spongy moth caterpillars killed by nucleopolyhedrosis virus (NPV) hang in an inverted “V” orientation; caterpillars killed by the fungus Entomophaga maimaiga hang vertically. / Photo Credit: Wisconsin DNR

By Michael Hillstrom, Wisconsin DNR Forest Health Specialist
Michael.Hillstrom@wisconsin.gov; 608-513-7690

Spongy moth caterpillars began hatching at the end of April in 2025 and are now actively feeding on leaves. In most Wisconsin locations, though, the population will not be as high as it has been in the last few years.

Wisconsin has had the largest outbreak in state history over the past few years. Fortunately, the outbreak collapsed in many areas of the state in 2024. The wet spring weather in April and May of 2024 allowed a fungus and a virus that infects spongy moth caterpillars to cause heavy mortality. Although some hot spots still exist in south central and northeast Wisconsin, we expect those populations to decline in 2025.

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Watch For Oak Wilt Symptoms

Posted on by akabelowsky
A wide-angle photo showing an oak tree in the center that died rapidly from oak wilt during the summer of 2024.

An oak tree (center) that died rapidly from oak wilt during the summer of 2024. / Photo Credit: Wisconsin DNR

By Michael Hillstrom, Wisconsin DNR Forest Health Specialist
Michael.Hillstrom@wisconsin.gov or 608-513-7690

Oak wilt symptoms typically begin to appear in southern Wisconsin in late June and in northern Wisconsin during July.

Watch for browning leaves, starting at the top of the canopy and progressing downward. Most leaves will fall from infected trees as they die, typically within two to four weeks.

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Take Action On Invasive Species This Month

Posted on by akabelowsky
Photo showing volunteers smiling while they spend a busy day pulling garlic mustard from a Wisconsin forested area.

Volunteers smile while they spend a busy day pulling garlic mustard from a Wisconsin forested area. Volunteers provide thousands of hours of annual help in the fight against invasive plant species. / Photo Credit: Wisconsin DNR

By Mackenzie Manicki, Wisconsin DNR Invasive Plants Specialist
Mackenzie.Manicki@wisconsin.gov or 608-206-4561

June is Invasive Species Action Month in Wisconsin. This tradition of spreading awareness and taking action began back in 2005.

Twenty years ago, the Wisconsin Invasive Species Council collaborated with partners such as the Wisconsin Department of Natural Resources (DNR) and the Invasive Plants Association of Wisconsin (IPAW) to hold the first Invasive Species Action Awards, aimed at recognizing and celebrating professional or volunteer groups and individuals that exemplify what it means to make an impact on invasive species.

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Invasives And Imposters: Native Look-Alikes To Know

Posted on by akabelowsky

By Wisconsin DNR

With 145 invasive plants regulated under Wisconsin’s Invasive Species Rule NR40, it can be challenging to identify some of these plants while out in the woods.

The task can be further complicated by the presence of native lookalikes – plants that have a similar appearance to harmful invasive species but are actually native plants that benefit wildlife, pollinators and ecosystems in Wisconsin.

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More Spruce Budworm Defoliation Expected

Posted on by akabelowsky
A close-up photo showing young spruce budworm larvae beginning to feed as buds break, causing the new growth to crook where feeding damage occurs. Webbing is also common.

Young spruce budworm larvae begin feeding as buds break, causing the new growth to crook where feeding damage occurs. Webbing is also common. / Photo Credit: Linda Williams, Wisconsin DNR

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

From early indications, the spruce budworm outbreak in some areas of northern Wisconsin is preparing to continue for yet another year.

During the third week of May, expanding buds on balsam fir trees were already showing damage from the tiny larvae.

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What’s That Under The Bark Of Red Pines?

Posted on by akabelowsky
A close-up photo showing pitch blobs near the base of a red pine, indicating attack by red turpentine beetle.

Pitch blobs near the base of a red pine indicate attack by red turpentine beetle. / Photo Credit: Linda Williams, Wisconsin DNR

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

Red turpentine beetle and pine root collar weevil are the most common insects found attacking near the base of red pine trees in Wisconsin, whether near ground level or just below ground level.

Here are some tips on identifying and controlling these pests.

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Forest Tent Caterpillar Outlook Stays Low

Posted on by akabelowsky
A close-up photo showing forest tent caterpillar larvae displaying gregarious behavior and feeding on a tree leaf.

Forest tent caterpillar larvae displaying gregarious behavior and feeding on a tree leaf. / Photo Credit: Paul Cigan, Wisconsin DNR

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

Forest tent caterpillar (FTC) populations do not appear to be making a significant return this growing season.

Spring egg mass surveys indicate that populations continue to remain low, continuing the longest documented interphase between outbreaks on state record, at 22 years and counting. The interphase provides some relief for the health of aspen stands recovering from several consecutive years of recent spongy moth defoliation.

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Red Pine And Hemlock Needles Suddenly Looking Brown

Posted on by akabelowsky
A photo showing hemlock needles affected by winter desiccation that have started browning at the needle tips and moving inward, sometimes killing the entire needle.

Hemlock needles affected by winter desiccation will start browning at the needle tips and move inward, sometimes killing the entire needle. / Photo Credit: Linda Williams, Wisconsin DNR

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

During the winter months, warm or sunny weather can wreak havoc on evergreen trees.

Conifers such as hemlock, pines and fir can lose moisture from their needles during the winter. If too much moisture is lost, those needles can quickly turn yellow or brown once the weather warms up in the spring.

Extensive browning of needles on hemlock — sometimes more than 50 percent of the needles – was observed in scattered areas of Oneida and Bayfield counties by the second week of April. The brown needles eventually dropped from the trees, leaving the remaining foliage looking very thin. Buds on the trees appeared viable, and the trees should break bud as normal.

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SilviCast Digs Into The Buckthorn Battle

Posted on by akabelowsky
The logo for the Silvicast, a podcast hosted by Wisconsin DNR silviculturists Greg Edge and Brad Hutnik and produced by the University of Wisconsin-Stevens Point's Wisconsin Forestry Center.

The logo for the Silvicast, a podcast hosted by Wisconsin DNR silviculturists Greg Edge and Brad Hutnik and produced by the University of Wisconsin-Stevens Point’s Wisconsin Forestry Center. / Graphic Credit: UW-Stevens Point

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

They talked about pulling it, smothering it, using herbicide on it, making turkey calls and making curtain rods from it.

They even wondered if they should just “kill it with fire.”

But it seems Midwestern foresters’ never-ending battle against buckthorn requires a brainier approach.

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DNR’s Hillstrom To Discuss Invasive Species

Posted on by akabelowsky
A photo of Michael Hillstrom, invasive forest pest coordinator for the Wisconsin Department of Natural Resources Forest Health team.

Michael Hillstrom, invasive forest pest coordinator for the Wisconsin Department of Natural Resources Forest Health team. / Photo Credit: Wisconsin DNR

By Wisconsin DNR

Michael Hillstrom, Invasive Forest Pest Coordinator for the Wisconsin Department of Natural Resources (DNR), will present a public talk on invasive species and forest health on Sunday, June 22.

Hillstrom’s talk will be part of a two-hour presentation, running from 10 a.m. to noon at Lake Kegonsa State Park, 2405 Door Creek Rd., Stoughton. It is open to the public.

The event is one of several statewide gatherings organized by the DNR as part of Invasive Species Awareness Weekend.