Southern WI Forest Health

Spruce Budworm Defoliation Continues

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

Closeup photo showing that webbing created by the spruce budworm caterpillar holds needles and frass and protects the caterpillar. A pupa hangs from the branch.

Webbing created by the spruce budworm caterpillar holds needles and frass and protects the caterpillar. A pupa hangs from the branch. / Photo Credit: Linda Williams, Wisconsin DNR

Although symptoms weren’t as prevalent as in 2023, this year marked yet another year of defoliation from spruce budworm.

Another severe year of defoliation causes additional stress on the trees. Even though there has been a lot of rainfall this spring, it’s still stressful for the trees to face repeated years of defoliation by spruce budworm before they begin to decline and die.

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Dropping Leaves May Indicate Oak Wilt

Posted on by akabelowsky

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

Photo showing that oak leaves that drop from a tree infected with oak wilt may be all brown or all green, or often they will have green near the base of the leaf and the outer portions will be brown or watersoaked green.

Oak leaves that drop from a tree infected with oak wilt may be all brown or all green, or often they will have green near the base of the leaf and the outer portions will be brown or watersoaked green. / Photo Credit: Linda Williams, Wisconsin DNR.

The middle of summer is the time to start watching oak trees for symptoms of oak wilt. Although symptoms show up suddenly and leaves drop quickly, symptoms can emerge anytime between now and when leaves turn color in the fall.

Trees that were wounded in the spring and became infected with the fungus that causes oak wilt will usually die that same year. In established oak wilt pockets, the fungus moves underground through grafted root systems and trees will wilt as the fungus moves into the tree.

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Tubakia Leaf Disease Affects Red Oak

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

A tree showing that lower branches are thin and have lost leaves due to Tubakia leaf spot, while leaves on its upper branches look good.

A tree showing that lower branches are thin and have lost leaves due to Tubakia leaf spot, while leaves on its upper branches look good. / Photo Credit: Linda Williams, Wisconsin DNR.

Tubakia leaf spot is a leaf disease caused by a fungus (Tubakia dryina) that typically affects the lower canopy of red oaks.

Because of all the rain that came during the spring and early summer of 2024, the fungus has started to impact some trees. Problems didn’t occur last year because the weather was too dry.

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Spongy Moth Status Update

Posted on by akabelowsky

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

A photo showing several trees with spongy moth defoliation in Marinette County in mid-June 2024.

Spongy moth defoliation in Marinette County in mid-June 2024. / Photo Credit: Darrek Sams, Wisconsin DNR

As of early July, we have seen a mix of live and dead caterpillars and tree defoliation that is typical of a late-stage spongy moth outbreak. Reports of defoliation have been received as far north as Florence County.

Recent aerial surveys in southern Wisconsin spotted defoliation in the same general areas as in 2023, but the defoliation has generally been less intense this year. Information for northern Wisconsin has yet to be made available. Refoliating oaks, growing a second set of pale-looking leaves, were seen in Walworth County in early July.

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‘Cicadapalooza’ Makes Noise In Lake Geneva

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Photo showing dozens of recently emerged cicadas rest on a tree trunk at Big Foot Beach State Park in Lake Geneva on May 30, 2024.

Dozens of recently emerged cicadas rest on a tree trunk at Big Foot Beach State Park in Lake Geneva on May 30, 2024. / Photo Credit: Sarah Wolski, Wisconsin DNR

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

Brood XIII periodical cicadas apparently love Lake Geneva. The Wisconsin hotspot for Brood XIII has again been the resort city of Lake Geneva, located just a few miles from the Illinois border. It experienced Wisconsin’s first emergence of the insects’ latest 17-year cycle on May 17. Cicadas remained active – noisily so – through late June.

The city of Lake Geneva, joined by the University of Wisconsin-Madison Entomology department, celebrated the insects’ return with Cicadapalooza, a family-friendly, free pop-up event on June 8 that included guided walking tours, presentations by UW-Madison entomologists, cicada merchandise, food and more.

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Watch For Spongy Moth Caterpillar Diseases

Posted on by akabelowsky

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

With this spring’s weather bringing above-average rainfall across most of Wisconsin, we will likely see moderate to heavy mortality of spongy moth caterpillars at many locations this summer.

Last year, the statewide May-June period was the third-driest since recordkeeping began in the late 1800s, according to the NOAA National Centers for Environmental Information. As a result, the effectiveness of the caterpillar-killing fungus, Entomophaga maimaiga, was limited. Spring 2024 is noticeably wetter, and thus, increased effectiveness of E. maimaiga is likely.

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Slime Mold: Mysterious And Amazing

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

What can learn new things, move toward and acquire food, remember where food was and what foods are preferred, figure out the shortest route through a maze, remember where it has traveled and seem to disappear as quickly as it first appeared?

It’s slime mold, of course!

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Avoid Ash Trees When Placing Deer Stands

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Photo of hunter climbing into tree-mounted deer stand.

It is important to place and maintain tree stands carefully as you prepare for the upcoming deer hunting season. / Photo Credit: Wisconsin DNR

By Bill McNee, Forest Health Specialist, Wisconsin DNR;
Bill.McNee@wisconsin.gov; (920) 360-0942

The Wisconsin Department of Natural Resources (DNR) cautions hunters to avoid placing deer stands in or near ash trees this deer hunting season.

Most ash trees in the southern half of Wisconsin, Door County and the Mississippi River counties are dead or dying from emerald ash borer infestation. Although emerald ash borer is not as widespread in other parts of the state, the invasive insect continues to be found at additional locations throughout the state and unreported infestations also are likely.

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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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Another Ash Pest Found In Northern Wisconsin

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Close-up photo of an adult cottony ash psyllid.

A close-up photo of an adult cottony ash psyllid feeding on an ash leaf. / Photo Credit: Steve Garske, Great Lakes Indian Fish and Wildlife Commission

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

As if black ash trees don’t have enough problems with emerald ash borer (EAB), another ash pest recently was found at several locations in northern Wisconsin.

In June, Great Lakes Indian Fish and Wildlife Commission (GLIFWC) staff noticed black ash with leaf curling and puckering, early leaf drop and dieback at one of their Climate Change Program’s long-term phenology study sites.

After working with DNR Forest Health staff to narrow down the possibilities, insect samples were collected and sent to P.J. Liesch, director of the University of Wisconsin-Madison Insect Diagnostic Laboratory, for official identification. He identified them as cottony ash psyllid.

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