Statewide Forest Health

Multiple Oak Defoliators Active Now

Photo of oak leafroller caterpillar on a leaf.

Oak leafroller caterpillars web leaves together as they feed. Photo: Wisconsin DNR.

Linda Williams, DNR Forest Health Specialist, Woodruff or 920-360-0665

Watch for defoliators in your oak trees this summer. You may have already heard news reports about spongy moth caterpillar populations being high this year, but there are some native caterpillars to watch for this year as well.

In 2022, oak leafroller caterpillars caused significant defoliation to oaks in areas of northeastern and northwestern Wisconsin, as well as in Blue Mound State Park. Many other areas experienced lesser amounts of defoliation from oak leafroller.

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Emerald Ash Borer Found In Polk County

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

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.

DNR Silviculturists Create Podcast

Photo of goats grazing in a woodlot.

Grazing goats can reach as high as six feet to munch on leaves, which they prefer to grasses and stems. Photo: Wisconsin DNR.

Art Kabelowsky, DNR Forest Health outreach and communications specialist or 608-335-0167

“Who do you know wants to rent a goat?”

Milwaukee television viewers of a certain age might recognize that twist on the old commercial slogan of automobile dealer Ernie Von Schledorn: “Who do you know wants to buy a car?”

Although Ernie is no longer around, the idea of having foresters use goat grazing to control interfering vegetation remains in use.

It’s a discussion worth talking about — and listening to.

Goat grazing was the topic of a recent edition of SilviCast, a monthly podcast about silviculture produced as part of a collaborative effort between the Wisconsin Department of Natural Resources (DNR) and the Wisconsin Forestry Center, based at the University of Wisconsin-Stevens Point.

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Forest Health Team Adds Two Specialists

Art Kabelowsky, DNR Forest Health outreach and communications specialist or 608-335-0167

Photo of Erika Segerson-Mueller and Carter Hellenbrand.

Erika Segerson-Mueller and Carter Hellenbrand, newly hired invasive plant program specialists with the Wisconsin Department of Natural Resources Forest Health team.

Carter Hellenbrand said he decided to pursue a career with the Wisconsin Department of Natural Resources (DNR) when a high school field trip sent him deep into the weeds, pulling buckthorn at Badfish Creek Wildlife Area near Oregon, Wisconsin.

On the other hand, Erika Segerson-Mueller’s respect for the DNR dates back to her youngest days.

Both have recently started work with the DNR’s Forest Health team as specialists in the forest invasive plants program.

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DNR Staff Gets Tree Injection Training

Photo of a tree marked with a ribbon for pesticide/fungicide injection.
Photo of a worker demonstrating a tree injection nozzle.

Cory McCurry, an arborologist with Rainbow Ecoscience, talks with DNR Parks and Forest Health employees while demonstrating the use of a nozzle component of the Q-Connect tree injection system currently in use at state properties. Photo: Wisconsin DNR.

Art Kabelowsky, DNR Forest Health outreach and communications specialist or 608-335-0167

LAKE GENEVA, Wisconsin — Fifteen employees of the Wisconsin Department of Natural Resources gathered at Big Foot Beach State Park on May 16 to learn more about using injections of systemic pesticides to protect the health of high-value trees at state properties.

Ten Wisconsin State Parks employees and five members of the DNR’s Forest Health team met with representatives of Rainbow Ecoscience and Bartlett Tree Experts to witness a demonstration of best practices for tree injections.

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Garlic Mustard Aphid Advances

Art Kabelowsky, DNR Forest Health outreach and communications specialist or 608-335-0167

Photo of garlic mustard aphids on a leaf.

Dozens of garlic mustard aphids feed on the underside of a garlic mustard leaf in Michigan. The small, dark aphids, originally from Europe, have been found in Wisconsin and other states after first being discovered in Ohio in 2021. Photo: Rebecah Troutman, Holden Forests and Gardens, Kirtland, Ohio.

A new tool in the effort to fight invasive garlic mustard appears ready to make its move in Wisconsin.

The garlic mustard aphid, Lipaphis alliariae, has been moving westward after being discovered in Ohio in 2021. Since then, isolated populations have also been found in Wisconsin, Connecticut, Massachusetts, Michigan and Minnesota.

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Douglas County Joins Spongy Moth Quarantine

A spongy moth larva eats a leaf.

A spongy moth larva eats a leaf.

By Paul Cigan, DNR plant pest and disease specialist or 715-416-4920

In early April, Douglas County became the 53rd Wisconsin county added to the state’s spongy moth quarantine list after a discovery that the invasive insect (formerly known as gypsy moth) had become established in the county.

The United States Department of Agriculture-Animal and Plant Health Inspection Service (USDA-APHIS) and the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) made the determination based on results of a monitoring program of adult moths and other life stages.

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Prepare — Spongy Moth Caterpillars To Return

By Bill McNee, DNR Forest Health Specialist, Oshkosh or 920-360-0942

Spongy moth caterpillars clustered below a sticky barrier.

Spongy moth caterpillars clustered below a sticky barrier. Photo: Mark Guthmiller, Wisconsin DNR

This June and July, spongy moth populations are predicted to reach damaging levels in parts of Wisconsin. Populations began to rise in 2020, and this is likely to be the third year of the pest outbreak in some regions of southern Wisconsin.

At present, damaging populations are expected to be most noticeable in southern counties, counties to the north of the city of Green Bay, and in far northern Wisconsin near Lake Superior. Additional areas are likely to have high populations that are more concentrated in size.

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Effects Of Winter Take Toll On Trees

A group of planted white pine saplings with varying amounts of brown needles caused by winter desiccation.

Minor to moderate damage to white pine needles caused by winter desiccation. Photo: Wisconsin DNR


By Michael Hillstrom, DNR Forest Health Specialist, Fitchburg

Winter damage is one of the most commonly reported tree issues in early spring. The damage may be minor, such as off-color needles that are quickly replaced, but could be as severe as partial- or whole-tree mortality.

Winter desiccation occurs when conifers begin photosynthesizing on warm, windy days in late winter or early spring. Conifers may dry out in these conditions if they use their stored water and cannot replace it because the ground is still frozen.

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USDA Seeks Donations Of Infested Ash Trees

By Kyle Loughlin, Field Team Lead, USDA-APHIS
or 734-732-0025

A window cut into a tree’s bark shows signs of emerald ash borer infestation.

USDA staff cut a ‘bark window’ in green ash to uncover signs of emerald ash borer. Photo: US Department of Agriculture

The U.S. Department of Agriculture (USDA) is asking Wisconsin landowners for help in the battle against emerald ash borer (EAB).

EAB is an invasive insect from Asia that was first introduced into the United States in 2002. Since its discovery, EAB has caused the death and decline of tens of millions of ash trees.

The USDA is asking Wisconsin landowners to donate live ash trees infested with EAB to support USDA’s biological control program. The staff will use the wood to rear EAB’s natural enemies, which will then be released in Wisconsin and 31 other EAB-infested states and Washington, D.C.

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