Northwest WI Forest Health

Eastern Tent Caterpillar Webs Common

Posted on by akabelowsky

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

Photo of web of eastern tent caterpillars.

Eastern tent caterpillars and their webs start out small but grow quickly. Photo: Linda Williams, Wisconsin DNR.

Have you seen trees along roadsides with white webs in them? Eastern tent caterpillars (ETC) are hatching and beginning to feed on host trees, including cherry, apple and crabapple.

Landowners and homeowners may notice the white silken tents forming in branch forks. Although they form unsightly nests, ETC is a native insect, so management is not typically necessary. Even completely defoliated trees will produce new leaves within a few weeks.

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Spongy Moth Focus Of Video, Webcast

Posted on by akabelowsky

Art Kabelowsky, DNR Forest Health outreach and communications specialist
Arthur.Kabelowsky@wisconsin.gov or 608-335-0167

Add “YouTube Influencer” to the long list of career accomplishments of Andrea Diss-Torrance, Ph.D.

With the spongy moth caterpillar population on the rise in many areas of Wisconsin this season, the Wisconsin Department of Natural Resources stepped into action last month.

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Emerald Ash Borer Found In Polk County

Posted on by akabelowsky
Photo of Emerald Ash Borer larvae in a tree

Emerald ash borer has been discovered in Polk County for the first time. The invasive pest now has been found in 68 of Wisconsin’s 72 counties. Photo: Wisconsin DNR.

Paul Cigan, DNR plant pest and disease specialist
715-416-4920 or Paul.Cigan@wisconsin.gov

Emerald ash borer (EAB) was detected for the first time in Polk County this spring, making it the 68th of Wisconsin’s 72 counties in which the invasive pest was found since it was first discovered in the state in 2008.

Several green ash trees with woodpecker flecking were observed in the roadside right-of-way along 100th Avenue in the Town of Osceola during field work.

Two larvae were collected from an infested tree and officially confirmed as EAB by a USDA-APHIS identifier on May 8, 2023.

No regulatory changes have resulted from this detection because EAB was federally deregulated on Jan. 14, 2021, and Wisconsin instituted a statewide quarantine in 2018.

EAB will continue to spread in northern Wisconsin, significantly impacting the ash resource. This is a good time to review the DNR’s updated emerald ash borer webpage for information and resource links on EAB, along with the DNR’s EAB Silviculture Guidelines to become familiar with or to refresh on ash stand management options.

DATCP, DNR, UW Extension and tribal partners continue to track EAB’s spread, sharing detection information through online maps available to Wisconsin’s citizens, private businesses and governmental entities. The goal is to aid in EAB readiness planning, pest management and biological control activities.

With more than 20 new city/town/village detections already reported statewide in 2023, map updates continue to occur on a biweekly basis. To see where EAB has been found in Wisconsin or to report new municipal detections, please visit the Wisconsin EAB online detections map or PDF map.

Spongy Moth Forecast Caution Issued

Posted on by akabelowsky

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

Photo of mature spongy moth caterpillar

Mature spongy moth caterpillar on a leaf. Photo: Bill McNee, Wisconsin DNR

Wisconsin Department of Natural Resources Forest Health staff are cautioning Wisconsin residents that the next two months could bring the worst spongy moth outbreak in more than a decade.

The caterpillars of this invasive insect prefer to feed on oak, birch, crabapple, aspen and willow leaves, but will also feed on many other tree and shrub species.

Southern Wisconsin and parts of the north are already in a high-population outbreak that is predicted to continue and spread. Populations have remained high due to a low incidence of caterpillar-killing diseases last summer. In addition, weather conditions in 2023 are favorable for the caterpillars and unfavorable for Entomophaga maimaiga, a fungus that kills spongy moth caterpillars.

Property owners are encouraged to examine their trees and take action.  Specifically:

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Look For Spongy Moth Egg Masses – Larger Outbreak Possible in 2023

Posted on by kirsten.biefeld

By: Bill McNee, DNR Forest Health Specialist, Oshkosh

bill.mcnee@wisconsin.gov or 920-360-0942

Three tan-colored spongy moth egg masses on a single tree branch in Walworth County.

Three spongy moth egg masses on a branch in Walworth County. Photo Credit: Bill McNee, Wisconsin DNR

Now that spongy moth* (formerly known as gypsy moth) egg laying is complete for 2022, it’s a good time to look for and dispose of egg masses produced by adult moths over the past two months.

Spongy moth egg masses are tan-colored lumps about the size of a nickel or quarter, and are found on trees, buildings and other outdoor objects. They may also be found in protected places such as firewood piles and birdhouses. Newly produced egg masses will feel firm and appear darker in color than older egg masses, which appear faded, feel spongy and do not contain viable eggs. The current-year egg masses will not hatch until next spring.

In 2022, Wisconsin’s spongy moth population grew for a third consecutive summer due to favorable weather conditions and limited caterpillar mortality from diseases. The outbreak was most dramatic in opposite ends of the state. In southern and southeast Wisconsin, several thousand oak-dominated acres were heavily defoliated and very large numbers of property owner reports were received by DNR staff. In Bayfield County, about 80,000 acres of rural defoliation was reported from aspen-dominated forests. Smaller patches of defoliation were also reported from several other counties. Continue reading “Look For Spongy Moth Egg Masses – Larger Outbreak Possible in 2023” →

EAB Found In Barron County

Posted on by patricialindquist

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

Emerald ash borer (EAB) has been discovered for the first time in Barron County, in the town of Lakeland. Dead and dying green ash were observed and larval specimens were subsequently lab-confirmed. Most of the green ash across a 20-acre area are either dead or dying from EAB attack.

Dead and dying green ash trees with characteristic woodpecker damage

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Be On The Lookout For Forest Tent Caterpillar

Posted on by patricialindquist

By Paul Cigan, DNR Forest Health Specialist, Hayward, Paul.Cigan@wisconsin.gov or 715-416-4920; and Bill McNee, DNR Forest Health Specialist, Oshkosh, Bill.McNee@wisconsin.gov or 920-360-0942

Forest tent caterpillar (FTC) may be making its way back onto the radar of northern Wisconsin property owners in the coming years, as some confirmed reports of defoliation in northern counties have trickled in. A native defoliator with a preference for aspen, oak and birch, this species undergoes periodic population outbreaks every six to 16 years. Widespread outbreaks can last for several years, causing heavy defoliation, reduced growth and temporary stress on affected trees. The last widespread outbreak ended in 2002.

Many forest tent caterpillars gathered together on a tree.

Forest tent caterpillar larvae displaying gregarious behavior on tree stem. Photo credit: Dane Gravesen

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Protect Oak Trees From Oak Wilt By Pruning After July, Not Before

Posted on by eleanorvoigt

By Don Kissinger, DNR Urban Forester, 715-348-5746 or Don.Kissinger@wisconsin.gov; Paul Cigan, DNR Forest Health Specialist, 715-416-4920 or Paul.Cigan@wisconsin.gov

The Wisconsin Department of Natural Resources (DNR) urban and forest health specialists recommend not pruning or cutting oaks from April through July to protect oak trees from the often fatal oak wilt disease.

The spring season often draws property owners outdoors to soak up rays of long-awaited sunlight, breathe in some fresh air and begin seasonal yard maintenance and cleanup projects. While spring is a time to dust off yard tools like rakes, shovels and weed clippers, when it comes to the health of oak trees, keeping those chainsaws and trimming tools a safe distance away will go a long way to ensure that your trees stay healthy for many more spring seasons to come.

Sap-feeding beetle on a diseased oak tree in Sawyer County.

Sap-feeding beetle on a diseased oak tree in Sawyer County.

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Treat Your Valuable Ash Trees Against Emerald Ash Borer

Posted on by eleanorvoigt

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

Property owners with healthy, valuable ash trees should consider treating them with insecticide this spring to protect against emerald ash borer (EAB). The 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. Now is an excellent time to consider insecticide protection because the treatments are typically done between mid-April and mid-May once leaves begin to return.

Treatments on already-infested ash trees are more likely to be successful if the trees have low or moderate levels of woodpecker damage.

An ash tree branch with bark missing after woodpeckers attacked it while looking for larvae to eat.

This ash tree branch in West Allis has been attacked by woodpeckers looking for larvae to eat.

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Look For Gypsy Moth Egg Masses And Prepare For Hatch; DATCP Slow-The-Spread Treatments Announced

Posted on by eleanorvoigt

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

Typically, gypsy moth egg masses hatch in April as temperatures warm. Now is a great time to do an egg mass inspection to look for unknown infestations and treat or remove any masses within reach. Each mass can result in 500 to 1,000 leaf-eating caterpillars.

Egg masses are tan-colored lumps and vary from about the size of a nickel to a quarter. They can be found on many outdoor surfaces such as tree trunks, the undersides of branches, buildings, rocks, fences, retaining walls, firewood piles and picnic tables.

Gypsy moth egg masses on the underside of a maple branch

Gypsy moth egg masses on the underside of a maple branch. 

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