Pests

DNR Urges Spring Spongy Moth Treatment Plans

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Carefully scraping spongy moth egg masses off trees and into a cup of soapy water will help to hold down caterpillar damage in 2025.

Carefully scraping spongy moth egg masses off trees and into a cup of soapy water will help to hold down caterpillar damage in 2025. / Photo Credit: Bill McNee, Wisconsin DNR

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

The Wisconsin Department of Natural Resources (DNR) encourages property owners to examine their trees for spongy moth egg masses and determine whether control measures are needed this spring.

Property owners who have oak, birch, crabapple, aspen, willow and linden (basswood) trees should be particularly watchful because the caterpillars of this invasive insect prefer these species. However, they will feed on many other kinds of trees and shrubs.

Continue reading “DNR Urges Spring Spongy Moth Treatment Plans” →

Treat Ash Trees Against Emerald Ash Borer This Spring

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A photo of an ash tree next to a park trail in Winnebago County showing damage from woodpeckers feeding on EAB larvae beneath the bark.

An ash tree next to a park trail in Winnebago County shows damage from woodpeckers feeding on EAB larvae beneath the bark. / Photo Credit: Bill McNee, Wisconsin DNR

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

Property owners with healthy, valuable ash trees are encouraged to treat them with insecticide this spring to protect against emerald ash borer (EAB).

The invasive pest is currently the most damaging threat to trees in Wisconsin, killing more than 99% of the ash trees it infests.

Continue reading “Treat Ash Trees Against Emerald Ash Borer This Spring” →

Squirrels Can Damage Trees During Late Winter

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Photo showing that squirrels have removed significant amounts of bark from a maple tree's trunk to get at the tasty cambium layer underneath.

Squirrels have removed significant amounts of bark from this maple to get at the tasty cambium layer underneath. / Photo Credit: Linda Williams, Wisconsin DNR

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

Squirrels can be fun to feed and fun to watch, but when they start damaging or killing your trees, well, that’s not so cute.

It’s the time of year when we start to have some warm days that allow sap to start moving in trees. If there are broken branches or damaged bark, the tree can drip sap. And that can attract squirrels.

Continue reading “Squirrels Can Damage Trees During Late Winter” →

Squirrel Or Porcupine Damage: How Do You Know?

Posted on by akabelowsky
Photo showing squirrel tooth marks on a tree. Squirrel tooth marks are small and look like narrow scratches where the animals have removed the tree’s bark.

Squirrel tooth marks are small and look like narrow scratches where the animals have removed the tree’s bark. / Photo Credit: Linda Williams, Wisconsin DNR

By Linda Williams, Forest Health Specialist

Linda.Williams@wisconsin.gov or 920-360-0665

If something chewed the bark off your tree, how would you go about determining the culprit?

Quite a few animals can damage bark on trees, from deer and bears to rabbits and mice. But the damage from squirrels and porcupines can look very similar, especially from a distance. So, how can you tell the difference?

Continue reading “Squirrel Or Porcupine Damage: How Do You Know?” →

Now Is Time To Seek Out Spongy Moth Egg Masses

Posted on by akabelowsky
Large egg masses are seen 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

It might be a bit chilly these days, but spring is coming. When the weather warms up, the annual return of spongy moth caterpillars will begin.

There’s a way for landowners to make a dent in the population of the hungry caterpillars: Get out now to locate and properly dispose of spongy moth egg masses, produced by adult moths last summer.

Continue reading “Now Is Time To Seek Out Spongy Moth Egg Masses” →

What Are Those White Fluffies On Trees?

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Lots of beech scale, covered in white wool, makes this tree’s bark look fluffy.

Lots of beech scale, covered in white wool, makes this tree’s bark look fluffy. / Photo Credit: Linda Williams, Wisconsin DNR

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

Last month, we introduced readers to the woolly alder aphid, which is easier to spot in the winter as the insects congregate on alder branches and grow strands of white, waxy material to cover themselves for winter.

But there are other white, fluffy things that you might notice on tree bark or branches as well.

Beech scale, the insect associated with beech bark disease, is covered in white wool and remains on the tree throughout the winter. In areas with high beech scale populations, the beech trees can be so white with insects that the bark looks white, like a birch.

Continue reading “What Are Those White Fluffies On Trees?” →

2024 Spongy Moth Review

Posted on by akabelowsky

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

A tree shows high numbers of spongy moth caterpillars, though the majority of the caterpillars have been killed either by virus (hanging in an inverted V) or fungus (hanging in a stretched line, head down). The virus and fungus helped to quell a potential outbreak in many areas of the state in 2024.

A tree shows high numbers of spongy moth caterpillars, though the majority of the caterpillars have been killed either by virus (hanging in an inverted V) or fungus (hanging in a stretched line, head down). The virus and fungus helped to quell a potential outbreak in many areas of the state in 2024. / Photo Credit: Bill McNee, Wisconsin DNR

As the 2023 spongy moth season ended, there were hopes for a return to colder and wetter conditions in 2024 so that the spongy moth outbreak would decline or even come to an end.

What wound up happening in Wisconsin was the “lost winter,” the warmest since recordkeeping began in 1895. Given this warmth, there were concerns that the widespread spongy moth outbreak would continue for a third consecutive summer, with good caterpillar survival, ongoing defoliation and high rates of tree mortality in already stressed forests.

Continue reading “2024 Spongy Moth Review” →

Cooperative Enlists Public To Make Tree Health A Snap

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

Screenshot of the main page of the TreeSnap app as seen on a mobile phone.

The main page of the TreeSnap app as seen on a mobile phone. / Photo Credit: TreeSnap.org

It takes more than a village to foster healthy forests. More than a township, a city and a county, too. Sometimes, even more than a state.

That’s why the Great Lakes Basin Forest Health Cooperative (GLB FHC) was formed four years ago by Holden Arboretum in Ohio and the U.S. Department of Agriculture Forest Service.

Geographically, the group’s region encompasses an area from New Jersey to Wisconsin. The Wisconsin Department of Natural Resources (DNR) is an active member.

Continue reading “Cooperative Enlists Public To Make Tree Health A Snap” →

Check Conifers For Invasive Adelgids

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Photo showing white, cottony hemlock woolly adelgid egg sacs on a hemlock branch.

White, cottony hemlock woolly adelgid egg sacs on a hemlock branch. / Photo Credit: Bill McNee, Wisconsin DNR

By Michael Hillstrom, DNR Forest Health Specialist, Fitchburg; Michael.Hillstrom@wisconsin.gov

Hemlock woolly adelgid (HWA) and balsam woolly adelgid (BWA) are invasive, aphid-like insects that cause tree mortality in North America. Neither has been found in Wisconsin so far, but they are likely to arrive at some point, as they have been confirmed in Michigan.

HWA (Adelges tsugae) is an invasive, sucking insect pest of hemlock trees. The white, cottony egg sacs of HWA can be seen on the undersides of hemlock branches at the base of needles year-round. HWA saliva enters the tree while feeding. The saliva is toxic and causes needle drop and twig dieback, progressing to tree mortality in 4-10 years.

Continue reading “Check Conifers For Invasive Adelgids” →

New Invasive Pest Discovered In Wisconsin

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

A closeup of an elm zigzag sawfly caterpillar consuming a leaf. The invasive insect, new to Wisconsin, was found on an elm tree near the Wisconsin Department of Natural Resources office in Oshkosh on July 16, 2024.

A closeup of an elm zigzag sawfly caterpillar consuming a leaf. The invasive insect, new to Wisconsin, was found on an elm tree near the Wisconsin Department of Natural Resources office in Oshkosh on July 16, 2024. / Photo Credit: Bill McNee, Wisconsin DNR

The invasive insect elm zigzag sawfly (Aproceros leucopada) has been detected in Wisconsin for the first time.

Following the initial Wisconsin discovery in Portage County on July 4. Through Aug. 12, the pest has since been detected in 17 Wisconsin counties. Continue reading “New Invasive Pest Discovered In Wisconsin” →