Pests

Watch For Spongy Moth Caterpillars And Tree Damage This Summer

Posted on by akabelowsky

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

Close-up of caterpillar feeding on a leaf.

A spongy moth caterpillar feeds on a leaf. / Photo Credit: Wisconsin DNR

Property owners are encouraged to monitor their trees for spongy moth larvae and damage this summer to determine whether control measures are needed.

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 “Watch For Spongy Moth Caterpillars And Tree Damage This Summer” →

Spruce Budworm Outbreak Continues In 2026

Posted on by akabelowsky

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

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

The spruce budworm outbreak is continuing for yet another year in some areas of northern Wisconsin.

Continue reading “Spruce Budworm Outbreak Continues In 2026” →

Forest Tent Caterpillar Outlook

Posted on by akabelowsky
Closeup of caterpillars on a tree.

Forest tent caterpillar larvae displaying gregarious, clustering behavior on a tree stem. / Photo Credit: Wisconsin DNR

By Paul Cigan, DNR Forest Health Specialist, Hayward
dnr.wisconsin.gov/topic/foresthealth/staff, 715-416-4920

Populations of forest tent caterpillar (FTC) are likely to remain low throughout northern Wisconsin this growing season, continuing a record 23-year statewide trend.

Spring egg mass surveys showed a low presence of overwintering egg masses, suggesting that any defoliation this season is likely to be localized. Overwintering egg masses present on the twigs of deciduous twigs and branch tips are counted during surveys to forecast FTC population density and the associated risk of heavy defoliation going into spring leaf-out.

Continue reading “Forest Tent Caterpillar Outlook” →

Forest Health Staffers Plan Appearances

Posted on by akabelowsky
A worker in the woods, holding a young tree to be planted.

Wisconsin DNR Forest Insect Pest Specialist Mike Hillstrom gives a presentation during a New Forester Training session in Marinette County in 2024. / Photo Credit: Bill McNee, Wisconsin DNR

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

Mike Hillstrom, the Wisconsin Department of Natural Resources Invasive Forest Pest Coordinator, will give a public presentation on forest invasive species from 10 a.m. to noon Saturday, June 20, at Lake Kegonsa State Park in Stoughton.

The talk will be part of the informational and educational events sponsored as part of the DNR’s Invasive Species Awareness Weekend.

Continue reading “Forest Health Staffers Plan Appearances” →

Upcoming Training

Posted on by janness

Photo Credit: Wisconsin DNR

* These training opportunities are provided as an information service only and do not constitute an endorsement from the Wisconsin Department of Natural Resources (DNR).

See below for training on urban forestry basics, tree risk fundamentals in Spanish, plant diseases and pests, invasive species, student apprenticeships, nut trees and other urban forestry resources. Continue reading “Upcoming Training” →

Look For Spongy Moth Egg Masses And Take Action

Posted on by akabelowsky
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

Posted on by akabelowsky
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” →

Upcoming Trainings

Posted on by janness

* These training opportunities are provided as an information service only and do not constitute an endorsement from the Wisconsin Department of Natural Resources (DNR).

See below for information on training topics and events, including tree diseases and treatments, pest management, landscaping, career advancement, invasive species, pruning, volunteer management, new research, partnerships and developing an urban forest management plan. Continue reading “Upcoming Trainings” →

Increased Tree Mortality Seen As Spongy Moth Outbreak Ends

Posted on by akabelowsky
Mature spongy moth larva on a tree at Potawatomi State Park in Door County, July 2025.

Mature spongy moth larva on a tree at Potawatomi State Park in Door County, July 2025. / Photo Credit: Wisconsin DNR

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

Wisconsin’s recent period of high spongy moth populations (an “outbreak”) came to an end in 2025, as the remaining known hotspots were aerially sprayed or naturally collapsed. Only a handful of large larvae were observed or reported by property owners.

Spongy moth populations are likely to be low across the state for at least the next few years. However, it is possible that some sites may experience a population increase before then, if local weather conditions are favorable for the insect.

Continue reading “Increased Tree Mortality Seen As Spongy Moth Outbreak Ends” →

Report Invasive Hemlock Insects This Winter

Posted on by akabelowsky
Small, white hemlock woolly adelgid eggs found on the needles of a tree in Bastian, Virginia, in 2017.

Small, white hemlock woolly adelgid eggs are found on the needles of a tree in Bastian, Virginia, in 2017. / Photo Credit: Bill McNee, Wisconsin DNR

By Mike Hillstrom, Forest Invasive Pest Coordinator, Fitchburg
Michael.Hilstrom@wisconsin.gov or 608-513-7690

Hemlock woolly adelgid (HWA) looms as a major threat to Wisconsin’s hemlock trees. As the infestation of these invasive, aphid-like insects spreads in Michigan and other states in the eastern United States, Wisconsin is preparing to respond when it arrives.

HWA is most evident in winter and spring as fluffy, white, woolly balls that are present at the base of hemlock needles. These fluffy, waxy balls cover adult female adelgids and eggs.

Continue reading “Report Invasive Hemlock Insects This Winter” →