Pest

Green, Sawyer Counties Added To Spongy Moth Quarantine

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Map of Wisconsin showing counties in yellow quarantine for spongy moth.

The updated map of spongy moth quarantined counties in Wisconsin, showing the April 15 addition of Green and Sawyer counties to the quarantined list. / Map Credit: Wisconsin DNR

By Wisconsin DNR

Green and Sawyer counties have become the latest additions to Wisconsin’s spongy moth quarantine, joining most eastern and central Wisconsin counties already considered to be infested by the invasive insect.

The announcement was made April 15 by the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP), based on trapping data collected last year.

Continue reading “Green, Sawyer Counties Added To Spongy Moth Quarantine” →

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” →

Take Precautions to Prevent Tick Bites

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An adult deer tick looks for a spot to attach. / Photo Credit: Wisconsin DNR

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

Adult blacklegged (deer) ticks are already active this year, as of March 2026. The adults start looking for a host as soon as it warms up to around 40 degrees Fahrenheit.

In Wisconsin, between 20-60 percent of adult ticks are infected with the bacteria that causes Lyme disease. However, the risk of getting Lyme disease is higher with bites from nymphal ticks, which are most abundant in June and July, because they are so tiny and difficult to find. While only 10-28 percent of nymphs are infected with the Lyme disease bacteria in Wisconsin, rapid removal of a tick can reduce the risk of infection because it takes at least 24 hours for the Lyme bacteria to spread.

Continue reading “Take Precautions to Prevent Tick Bites” →

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” →

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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Look For Spongy Moth Egg Masses And Take Action

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Closeup of a person scraping spongy moth egg masses into a cup.

A putty knife, plastic knife or similar object can be used to gently scrape spongy moth egg masses into a cup of soapy water. The water can be discarded after two days. / Photo Credit: Wisconsin DNR

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

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 “Look For Spongy Moth Egg Masses And Take Action” →

Watch For Squirrel, Porcupine Damage In Spring

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Closeup of small squirrel tooth marks on a tree's mainstem.

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

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

As winter transitions into spring, you may notice patches of tree bark that have been removed. But what did the damage?

Several animals, including squirrels and porcupines, can chew or strip bark from trees. This can occur on hardwoods and conifers, older trees and young saplings. Damage can be enough to kill branches or even the entire tree.

Continue reading “Watch For Squirrel, Porcupine Damage In Spring” →

Does Cold Weather Bug The Bugs?

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A map of Wisconsin showing cold temperatures on Jan. 25, 2026.

Cold temperatures across the state of Wisconsin on Jan. 25, 2026. / Graphic Credit: National Weather Service

By River Mathieu, DNR Forest Health Specialist, Fitchburg
River.Mathieu@wisconsin.gov or 608-772-2758

Wisconsin experienced a polar vortex in late January 2026, and temperatures got chilly throughout the state, even reaching close to -40⁰ F in some places! Although it has warmed up, the cold weather is still fresh in everyone’s minds, leaving insect and forest lovers alike wondering how insects survive temperatures that cold.

The Wisconsin Department of Natural Resources Forest Health staff has received several questions over the past month about how insects survive cold weather in winter and whether the January temperatures were cold enough to kill insect pests.

Continue reading “Does Cold Weather Bug The Bugs?” →

Protect Valuable Ash Trees Against Emerald Ash Borer

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An ash tree in Oshkosh shows damage from woodpeckers feeding on emerald ash borer larvae beneath the bark.

An ash tree next to a walking trail in Oshkosh has been damaged by woodpeckers feeding on emerald ash borer larvae beneath the bark. / Photo Credit: Wisconsin DNR

By Bill McNee, DNR Forest Health Specialist, Oshkosh
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.

Woodpecker damage during the winter is often the first sign that an ash tree is infested. The birds remove pieces of bark while feeding on EAB larvae inside the tree. Insecticide treatment of infested ash trees is more likely to be successful if the trees have low or moderate levels of woodpecker damage.

Continue reading “Protect Valuable Ash Trees Against Emerald Ash Borer” →

Wisconsin Sees First Recovery Of EAB Parasitoid Oobius Agrili

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A plastic pan trap for wasps is hung from a tree branch.

A yellow pan trap used for trapping Oobius agrili wasps. / Photo Credit: United States Department of Agriculture Animal and Plant Health Inspection Service

By River Mathieu, DNR Forest Health Specialist
River.Mathieu@wisconsin.gov or 608-772-2758

One small adult wasp collected by United States Department of Agriculture Animal and Plant Health Inspection Service (USDA APHIS) staff at Riedel Redmond Nature Preserve in Mosinee (Marathon County) was recently identified as Oobius agrili.

USDA APHIS staff collected several wasp specimens in yellow pan traps and sent them to a U.S. Forest Service expert for identification. This marks the first recovery of O. agrili in Wisconsin.

Oobius agrili is an emerald ash borer (EAB) parasitoid that was first released in Wisconsin in 2011 and has been released annually since then. O. agrili parasitizes EAB eggs on the bark of ash trees, consuming the EAB larvae inside the egg. Continue reading “Wisconsin Sees First Recovery Of EAB Parasitoid Oobius Agrili” →