Pests

Don’t Let Tree Trouble Hitch A Ride On Firewood

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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.

Continue reading “Don’t Let Tree Trouble Hitch A Ride On Firewood” →

Oak Mortality Increases In 2023

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Photo of a bur oak tree more than 100 years old showing canopy dieback and epicormic branching due to twolined chestnut borer

A bur oak more than 100 years old exhibits canopy dieback and epicormic branching caused by twolined chestnut borer. / Photo Credit: Wisconsin DNR

By Michael Hillstrom, DNR Forest Health Specialist, Fitchburg
Michael.Hillstrom@wisconsin.gov

White, red and bur oaks have been experiencing increased mortality in Wisconsin and neighboring states over the last few years.

The causes of mortality are varied, but two-lined chestnut borer (TLCB) is the most common culprit. Wisconsin has switched from a period of historically wet years (2017-2020) to drought conditions that have become more severe each year (2021-2023). Add in frost damage, storm damage, increased growing season length and aging forests and the environmental recipe exists for stressed oaks that are more susceptible to attack by insects and diseases.

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Article Sets Record Straight On Value Of EAB Management

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Photo of an adult emerald ash borer beetle on a tree trunk

An adult emerald ash borer beetle on a tree trunk. The invasive insect is expected to eventually kill 99 percent of ash trees in Wisconsin. / Photo Credit: Bill McNee, Wisconsin DNR

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

Entomology Today magazine has published an article debunking common misconceptions about management of emerald ash borer (EAB). The information in the article can be helpful to communities and landowners deciding whether to invest in treatment to preserve ash trees.

The article focuses on treatments for high-value trees, not those in woodlands. The advice in the summary is clear for communities, property managers of high-use recreational lands and homeowners with ash near residences:

“Allowing nature to take its course is a budget-busting option.”

Continue reading “Article Sets Record Straight On Value Of EAB Management” →

Pink-Striped Oakworm Population Remains Low

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Photo of a pink-striked oakworm caterpillar on a hand.

This large caterpillar, a pink-striped oakworm, has great camouflage and blends in with oak twigs very well. / Photo Credit: Linda Williams, Wisconsin DNR

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

Pink-striped oakworm is a native fall defoliator. Fall defoliators affect the health of trees less than defoliators that occur in the spring.

Although literature states that high populations of this caterpillar can create significant defoliation, no defoliation was noted in the area this caterpillar was observed in Oneida County.

Continue reading “Pink-Striped Oakworm Population Remains Low” →

Aphids Make Sticky Situation For Oak, Beech Trees

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Photo of Myzocallis oak aphids on a leaf, with an adult at the left.

Myzocallis aphids feed on the top side of oak leaves. An adult is pictured on the left. / Photo Credit: Linda Williams, Wisconsin DNR

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

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

Aphids — and the honeydew they produce — have made their mark on trees in Wisconsin during 2023.

Midway through the summer, oak trees in areas of Vilas and Oneida counties were buzzing with activity. During September, beech trees in eastern Wisconsin became busy with a different species of aphid.

A look at the two situations:

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Pine Bark Adelgids Infest White Pines

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Photo of pine bark adelgids covered in white, waxy fluff on a white pine tree.

Pine bark adelgids covered in white, waxy fluff on a white pine tree. / Photo Credit: Wisconsin DNR

Michael Hillstrom, DNR Forest Health Specialist, Fitchburg
Michael.Hillstrom@wisconsin.gov

Pine bark adelgids are tiny, aphid-like insects that suck the sap of white pines. The bugs protect themselves from predators with a fluffy, white wax covering. Pine bark adelgids generate concern when thousands of them gather on white pines to feed, making the pine bark appear covered with sap.

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Spongy Moth Forecast Caution Issued

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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:

Continue reading “Spongy Moth Forecast Caution Issued” →

Douglas County Joins Spongy Moth Quarantine

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A spongy moth larva eats a leaf.

A spongy moth larva eats a leaf.

By Paul Cigan, DNR plant pest and disease specialist
Paul.Cigan@wisconsin.gov 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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Aerial Spraying Coming To Four State Properties

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

Spray aircraft used in spongy moth control

Spray aircraft used in spongy moth control. Photo: Bill McNee, Wisconsin DNR

The Wisconsin Department of Natural Resources (DNR) is taking action in the coming weeks in its battle against spongy moth (formerly known as gypsy moth) caterpillars.

An airplane will spray parts of four DNR properties to reduce the population of the hungry pest.

This year, high numbers of spongy moths threaten to strip trees of their leaves and may even kill high-value trees at these properties.

Continue reading “Aerial Spraying Coming To Four State Properties” →

Emerald Ash Borer Found In Vilas County

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Adult emerald ash borer beetle.

Adult emerald ash borer beetle. Photo: Wisconsin DNR.

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

Vilas County has the dubious distinction of becoming the first new Wisconsin county in 2023 to have a discovery of emerald ash borer (EAB).

EAB continues to spread into areas of northern Wisconsin. The first Vilas County detection was in the town of Lincoln. Additional infested trees have since been found in the town of Cloverland and the city of Eagle River. Continue reading “Emerald Ash Borer Found In Vilas County” →