The Dangers And Costs Of Infested Ash Trees

Credit: Joseph O’Brien, USDA Forest Service,

The emerald ash borer (EAB) will kill nearly all of Wisconsin’s ash trees that are not protected by insecticides. To help the public understand why it’s important to act against EAB, the DNR created a publication aimed at homeowners that addresses the dangers and costs of infested ash trees. Urban forestry professionals may wish to share this flyer with those who ask questions on these topics.

The key message of the publication is this: It’s crucial to decide ASAP whether to protect your ash trees with insecticides or have them removed. Either way, time is of the essence. If you delay in treating your ash trees, the treatment may be less effective. And if you wait to remove them, removal costs will be greater and safety hazards will only get worse.

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Eau Claire And Richland Counties Now Added To The Gypsy Moth Quarantine

By Andrea Diss Torrance, Invasive Insects Program Coordinator,, 608-516-2223

Gypsy moth has moved slowly across Wisconsin in the last 30 years since gaining a foothold in the counties along Lake Michigan. This month, the Animal and Plant Health Inspection Service and the Department of Agriculture, Trade and Consumer Protection (DATCP) determined that the invasive pest has become established in Eau Claire and Richland counties and have extended the quarantined area to include them.  This is the first time since 2015 that new counties have been added to the quarantine. Fifty-two of Wisconsin’s 72 counties are now quarantined for gypsy moth.

Wisconsin Gypsy Moth Quarantined Counties

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New Factsheets And Webpage Now Available

By Elly Voigt, DNR Forest Health Lab Technician.

The Wisconsin DNR’s Forest Health Team has recently released four new factsheets and a new webpage. The new factsheets are on the following topics:

Armillaria root disease

Beech bark disease

Peach bark beetle and cherry scallop shell moth

Hemlock woolly adelgid

Hemlock Woolly Adelgid Forest Health Factsheet

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Updated Emerald Ash Borer Treatment Guides Now Available

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

The University of Wisconsin-Madison Extension has recently updated two insecticide guides for those interested in treating high-value ash trees against emerald ash borer (EAB). One guide lists options for homeowners and the other lists options for tree-care professionals. Download the guides here.

First page of the homeowner guide to EAB insecticide treatments.

First page of the homeowner guide to EAB insecticide treatments.

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Keep An Eye Out For Beech Leaf Disease

By Elly Voigt, DNR Forest Health Lab Assistant, Fitchburg

Beech leaf disease (BLD) is a destructive disease affecting beech trees in the U.S. The disease has not yet been observed in Wisconsin, but it could become an issue in the future in the eastern third of the state, which is the edge of the American beech’s native range.

Figure 1. Symptomatic banding on beech foliage, as well as asymptomatic leaves. Photo: Ohio State University Extension

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It’s Camping Season! Where Can I Get Firewood?

By Andrea Diss-Torrance, DNR Invasive Forest Insects Program Coordinator,, 608-516-2223

Most people know that using locally-sourced firewood helps prevent the spread of invasive pests and diseases. What may be less well known are the processes for finding local sources of firewood or learning where and how you can collect it yourself.

A set of images showing an oak wilt spore pad, an emerald ash borer beetle emerging from a tree and a gypsy moth caterpillar on a leaf.

In Wisconsin, oak wilt, emerald ash borer, gypsy moth and several other invasive pests and diseases are moved in or on firewood. During the camping season, these pests can emerge from transported wood to attack trees at the camper’s destination. Photo credit: Wisconsin DNR, MJ Raupp Bugwood, WDNR

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The Tick App: ‘Your On-the-Go Tick Expert’

By Danielle Smith, Midwest Center of Excellence for Vector-Borne Disease, UW-Madison

Researchers at the University of Wisconsin-Madison, Columbia University and Michigan State University have developed the TickApp, a mobile smartphone application that allows users to learn how they can protect themselves, their families and their pets from ticks—and join a team of citizen scientists helping researchers better understand ticks and tick-borne disease risk.

Adult blacklegged tick on a dead leaf.

Adult blacklegged tick

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Emerald Ash Borer Detected In Langlade County

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

Emerald ash borer (EAB) has been identified in Langlade County. Although this is the first find of EAB in Langlade County, it was found in three separate areas of the county in the towns of Ainsworth, Parrish and Wolf River. Two of these locations were within the area hit by the derecho storms in July 2019.

This was the first new county EAB detection for 2021 and is the 59th county in Wisconsin to identify the insect. There are no regulatory changes due to these detections since EAB was federally deregulated as of January 14, 2021, and Wisconsin instituted a state-wide quarantine in 2018.

Check out the interactive Wisconsin map showing which Townships and Municipalities are known to have EAB.

Bark removed using hatchet to show EAB larval galleries underneath.

Bark removed using hatchet to show EAB larval galleries underneath.

Balsam Gall Midge Swellings On Fir Needles

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

If you notice swollen needles or bare branches on balsam fir trees this spring, the culprit might be balsam gall midge. Adult balsam gall midges are tiny flies that lay their eggs in the developing new shoots shortly after budbreak in the spring.

Balsam fir needles with swellings caused by balsam gall midge will turn brown and drop from the tree prematurely.

Balsam fir needles with swellings caused by balsam gall midge will turn brown and drop from the tree prematurely.

Trees with late-breaking buds are less susceptible to gall midge attacks, as the buds are still tight when adult midges are laying eggs. The young larvae feed at the base of developing needles, causing needle tissue to grow around them (forming the needle gall).

The galls are green during the spring and summer but turn yellow in early fall, and infested needles drop prematurely. In the fall, the mature larvae drop to the ground, where they overwinter in the litter. By early the following spring, most of the damaged needles have fallen off, leaving bare spots along the branches where no needles are present.

Control options using insecticide applications are geared towards Christmas trees and are generally not necessary for forest trees.

Treat Your Valuable Ash Trees Against Emerald Ash Borer

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

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

Municipal foresters and property owners with healthy, valuable ash trees should consider treating the trees 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 percent of the ash trees it infests. 

Woodpecker damage during the winter is often the first sign that an ash tree is infested, so it is essential to examine your ash trees. Now is an excellent time to consider insecticide protection because the treatments are usually 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.

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