Statewide Forest Health

Maple Petiole Borer Sawfly Causing Leaf Drop

Posted on by akabelowsky
A closeup display photo showing prematurely fallen sugar maple leaves that have a normal appearance, except for characteristic darkened petiole stubs caused from feeding damage of the maple petiole borer.

Prematurely fallen sugar maple leaves with normal appearance except for characteristic darkened petiole stubs caused from feeding damage of the maple petiole borer. / Photo Credit: Paul Cigan, Wisconsin DNR

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

Fallen maple leaves have been observed under Wisconsin maple trees since late May.

The fallen leaves are typically of normal shape, size and color, but have a darkened petiole stub (i.e., leaf stem) remaining. A closer examination of the petiole may reveal a hollow feeding tunnel containing tiny larvae of the insect responsible for the damage inside: the maple petiole borer.

Continue reading “Maple Petiole Borer Sawfly Causing Leaf Drop” →

Anthracnose Infecting Hardwood Leaves

Posted on by akabelowsky
Photo of ash leaves infected with anthracnose.

Ash leaves infected with anthracnose. / Photo Credit: Wisconsin DNR

By Michael Hillstrom, DNR Forest Health Specialist
Michael.Hillstrom@wisconsin.gov
and Abby Krause, DNR Urban Forestry Coordinator
Abigail.Krause@wisconsin.gov

Anthracnose is a common disease of hardwood trees during cool, wet spring seasons. Some parts of Wisconsin have been cooler and wetter than others this spring, so anthracnose damage may be patchy.

Ash, maple, white oak, sycamore and walnut are the most impacted tree species. Each species has its own species of anthracnose that infects it, but if weather conditions are right, then we tend to see damage on multiple species.

Continue reading “Anthracnose Infecting Hardwood Leaves” →

DNR Debuts Fact Sheet On White Grubs

Posted on by akabelowsky
Closeup photo showing a white grub in topsoil, feeding on a root.

A white grub feeds on a root. / Robert L. Anderson, USDA Forest Service, Bugwood.org

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

White grubs, the larvae of Wisconsin’s native May/June beetles (Phyllophaga spp.), can cause significant damage to forest plantings.

To help those who plan to plant seedlings and saplings, the Wisconsin Department of Natural Resources’ (DNR) Forest Health team has produced a fact sheet on white grubs, aimed specifically at forest plantings.

Continue reading “DNR Debuts Fact Sheet On White Grubs” →

Wild Cucumber Will Catch Your Attention

Posted on by akabelowsky
A photo showing star-shaped leaves, pale flowers and cucumber fruit, all characteristics of wild cucumber.

Star-shaped leaves, pale flowers and cucumber fruit, all characteristics of wild cucumber. / Photo Credit: Bugwood.org

By the Wisconsin Department of Natural Resources

Plants that are pokey, viny or quick to spread across the landscape sometimes seem alarming when you discover them in your backyard or woods, or even when you spot them along the highway.

Wild cucumber has all these characteristics, and its growth rate has been quite prolific in some parts of Wisconsin again this year. But all of this is not as ominous as it seems.

Continue reading “Wild Cucumber Will Catch Your Attention” →

Anthracnose Infecting Hardwood Leaves

Posted on by janness

By Michael Hillstrom, DNR Forest Health Specialist; Michael.Hillstrom@wisconsin.gov
and Abby Krause, DNR Urban Forestry Coordinator; Abigail.Krause@wisconsin.gov

Oak leaves infected with anthracnose.

Anthracnose is a common disease of hardwood trees during cool, wet spring seasons. Some parts of Wisconsin have been cooler and wetter than others this spring, so anthracnose damage may be patchy.

Ash, maple, white oak, sycamore and walnut are the most commonly impacted tree species. Each species has its own species of anthracnose that infects it, but if weather conditions are right, then we tend to see damage on multiple species. Continue reading “Anthracnose Infecting Hardwood Leaves” →

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.

Continue reading “Spongy Moth Population In Decline” →

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.

Continue reading “Take Action On Invasive Species This Month” →

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.

Continue reading “What’s That Under The Bark Of Red Pines?” →

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.

Continue reading “SilviCast Digs Into The Buckthorn Battle” →

Rotstop® C No Longer Available In North America

Posted on by akabelowsky
Photo of a worker manually applying fungicide, imbued with blue dye, to a freshly cut tree stump to fight the spread of fungal diseases such as Heterobasidion root disease.

A worker manually applies fungicide, imbued with blue dye, to a freshly cut tree stump to fight the spread of fungal diseases such as Heterobasidion root disease. / Photo Credit: Wisconsin DNR

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

The manufacturer, Lallemand Plant Care, recently decided to remove Rotstop® C fungicide from the North American market.

As a result, the product is no longer available for purchase in North America. If you already have the product and have stored it in an appropriate space, you may still use it as a preventative treatment for Heterobasidion root disease (HRD) as long as the expiration date has not arrived.

Continue reading “Rotstop® C No Longer Available In North America” →