spongy moth

After A Quiet Year, Conduct Spongy Moth Egg Mass Surveys This Fall

Posted on by akabelowsky

The only mature spongy moth caterpillar detected at Harrington Beach State Park in Ozaukee County in July 2026 crawls up a tree’s mainstream. / Photo Credit: Wisconsin DNR

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

Wisconsin’s recent period of high spongy moth (Lymantria dispar) populations came to an end in 2025 and the population remained very low in 2026.

Only a handful of caterpillar reports were received, most often coming from southern Jefferson County and eastern Dane County. Most notably, numerous bur oaks were reported to be infested with several hundred caterpillars per tree in and around Cambridge, Fort Atkinson and Lake Mills; light feeding damage was visible.

Continue reading “After A Quiet Year, Conduct Spongy Moth Egg Mass Surveys This Fall” →

Green, Sawyer Counties Added To Spongy Moth Quarantine

Posted on by akabelowsky
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.

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Landowners Urged To Fight Spongy Moth

Posted on by wjaroch

A closeup of a fresh spongy moth egg mass on a tree. Now is the time to locate and destroy egg masses to reduce the number of caterpillars attacking your trees in the spring. / Photo Credit: Bill McNee, Wisconsin DNR

As fall begins, landowners all over Wisconsin – including those involved in the Wisconsin Department of Natural Resources (DNR) Managed Forest Law program – are urged to remember the fight against spongy moths.

After all, the best time to put a dent in next year’s infestation is to spend some time during fall and winter finding and removing spongy moth egg masses – each of which contains 500 or more potential future caterpillars.

The invasive pest caused a state-record defoliation total of 373,000 acres in 2023. The outbreak seemed on track to continue in several areas of the state in 2024 until rain and cooler weather boosted the emergence of two natural enemies of spongy moth caterpillars, a virus and a fungus, which helped to greatly reduce the population in many areas last July.

Still, caterpillars survived to pupate, mate and leave behind egg masses that will become next spring’s batch of caterpillars. Fortunately for landowners, the next few months mark the best opportunity to attack the spongy moth population, eliminating the caterpillars before they have a chance to emerge and feed. Continue reading “Landowners Urged To Fight Spongy Moth” →

Reminders About Spongy Moth Quarantine

Posted on by akabelowsky

By Meg Sanders, Wisconsin Department of Agriculture, Trade and Consumer Protection;
MeganT.Sanders@wisconsin.gov or 715-891-8158

The state Department of Agriculture, Trade and Consumer Protection (DATCP) works with the U.S. Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS) to enforce a spongy moth quarantine in Wisconsin, with the goal of limiting the spread of the spongy moth to new, uninfested areas.

The quarantine now covers 53 of Wisconsin’s 72 counties. The quarantine regulates woody nursery stock, Christmas trees, firewood, logs and outdoor household items. Quarantine regulations apply to businesses and private citizens.

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Spongy Moth Status Update

Posted on by akabelowsky

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

A photo showing several trees with spongy moth defoliation in Marinette County in mid-June 2024.

Spongy moth defoliation in Marinette County in mid-June 2024. / Photo Credit: Darrek Sams, Wisconsin DNR

As of early July, we have seen a mix of live and dead caterpillars and tree defoliation that is typical of a late-stage spongy moth outbreak. Reports of defoliation have been received as far north as Florence County.

Recent aerial surveys in southern Wisconsin spotted defoliation in the same general areas as in 2023, but the defoliation has generally been less intense this year. Information for northern Wisconsin has yet to be made available. Refoliating oaks, growing a second set of pale-looking leaves, were seen in Walworth County in early July.

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Don’t Let Tree Trouble Hitch A Ride On Firewood

Posted on by akabelowsky
Photo of spongy moth egg masses attached to a piece of firewood

A pair of spongy moth egg masses attached to a piece of firewood. Moving this firewood to another site could put trees at that site at risk in the spring. / Photo Credit: Wisconsin DNR

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

Are you generally hesitant to give hitchhikers a free ride?

October was National Firewood Awareness Month, and even though November has arrived, the Wisconsin Department of Natural Resources (DNR) continues to urge residents and visitors to follow the same line of thinking when it comes to moving firewood.

That’s because tree-killing hitchhikers often lurk on or in firewood — including spongy moth, emerald ash borer, the fungus that causes oak wilt and other invasive insects and fungi. When untreated, infested firewood is transported away from where the tree died, those pests and fungi can later emerge to attack trees at the new site. This can happen whether that new location is in the next town or hundreds of miles away.

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DNR Debuts Video On Scraping Spongy Moth Egg Masses

Posted on by akabelowsky
Photo of Wisconsin DNR's Andrea Diss-Torrance scraping a spongy moth egg mass off a tree.

Wisconsin DNR invasive forest insects program coordinator Andrea Diss-Torrance demonstrates scraping a spongy moth egg mass off a tree while making a video on the subject for the DNR. / Photo Credit: Wisconsin DNR

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

The fall and winter months present a perfect opportunity to protect trees by searching out and removing spongy moth egg masses.

The invasive insects currently exist only as tiny eggs, camped out in egg masses that can be found in places such as tree trunks and branches, under park picnic benches and swing sets, and under the awnings of buildings.

And now, the Wisconsin Department of Natural Resources (DNR) has debuted a short video showing exactly how to easily and safely remove egg masses to reduce next spring’s population of hungry spongy moth caterpillars.

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Time To Seek Out Spongy Moth Egg Masses

Posted on by akabelowsky

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

Photo of spongy moth egg masses on a tree.

Three spongy moth egg masses are found on a tree branch at Kettle Moraine State Forest Southern Unit in Walworth County. / Photo Credit: Bill McNee, Wisconsin DNR

The Wisconsin Department of Natural Resources (DNR) is encouraging property owners to seek out and dispose of spongy moth egg masses, which were produced by adult moths during the summer.

Each spongy moth egg mass contains hundreds of eggs that will hatch into hungry, leaf-eating caterpillars in the coming spring. Large numbers of these invasive caterpillars can be a tremendous nuisance that may cause tree mortality.

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Forest Health Team Offers Seven New Fact Sheets, Updates Website

Posted on by akabelowsky
A preview of the new Wisconsin Department of Natural Resources Forest Health fact sheet on spongy moth.

A preview of the new Wisconsin Department of Natural Resources Forest Health fact sheet on spongy moth. Graphic Credit: Wisconsin DNR

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

The Wisconsin Department of Natural Resources’ (DNR) Forest Health team has debuted seven new fact sheets, providing information on various forest insects and diseases as well as tips on how to deal with their emergence on your property.

The new fact sheets provide details on spongy moth, oak wilt management, spruce budworm, jack pine budworm, tamarack insects (larch casebearer and eastern larch beetle), red pine pocket decline and mortality and a comparison of common spring defoliator caterpillars (forest tent caterpillar, eastern tent caterpillar and spongy moth).

Additionally, the Forest Health team has updated and/or refreshed the look of its 13 existing fact sheets.

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