Woodland owners

Winter Squirrel Damage Killing Maple Branches

Posted on by akabelowsky

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

Two photos show maple branches that died recently due to previous damage from squirrels.

Two photos show maple branches that died recently due to previous damage from squirrels. / Photo Credit: Linda Williams, Wisconsin DNR

Have you noticed maple branches suddenly dying this summer?

Sudden mortality of maple branches during the summer in northern Wisconsin is often a result of squirrel damage that occurred in late winter and early spring.

In late winter and early spring, gray squirrels strip the bark of maples to get at the sweet maple sap. When the damage is extensive or severe, entire trees or branches will be killed immediately and will not leaf out in the spring.

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Japanese Beetles Finding New Locations

Posted on by akabelowsky

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

A closeup photo of Japanese beetles defoliating basswood leaves. The invasive pest is becoming more prevalent in northern Wisconsin.

A closeup photo of Japanese beetles defoliating basswood leaves. The invasive pest is becoming more prevalent in northern Wisconsin. / Photo Credit: Linda Williams, Wisconsin DNR

The Japanese beetle (Popillia japonica) is an invasive insect that feeds on many plant species. The pests “skeletonize” leaves by eating the material between the veins.

Adult Japanese beetles feed on the flowers and leaves of more than 300 plant species, including trees, shrubs and herbaceous plants. Forest trees can be defoliated, with open-grown or edge trees suffering the highest defoliation rates.

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Jack Pine Budworm Outbreak Subsides

Posted on by akabelowsky

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

Aerial view of jack pine budworm defoliation in jack pine stands in Douglas County during the 2023 outbreak. / Photo Credit: Paul Cigan, Wisconsin DNR

Jack pine defoliation caused by the jack pine budworm (JPBW) continued at mostly light levels this year, affecting stands in the Central and Northwest Sands Ecological Regions of Wisconsin.

In the Northwest Sands, jack pine stands experienced light and scattered defoliation across Burnett, Douglas, Polk and Washburn counties. In the Central Sands, JPBW caused moderate to heavy defoliation across roughly 500 acres of jack pine on county and state forests in Jackson County, east of Black River Falls.

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Oak Decline Continues In Southern Wisconsin

Posted on by akabelowsky

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

Oak decline at Big Foot Beach State Park caused by flooding, drought, spongy moth defoliation, twolined chestnut borer and Armillaria. / Photo Credit: Michael Hillstrom, Wisconsin DNR

Bur and white oaks, most of them more than 100 years old, have experienced rapid mortality (within one to two years) over the past four years in southern Wisconsin and neighboring states. Research into the cause is ongoing, but the evidence so far suggests it’s an oak decline.

Oak declines are not caused by a single issue, but rather by the stacking of multiple health issues. Drought, flooding, storm damage, age, twolined chestnut borer, Armillaria and other root pathogens, and spongy moth and oak leafroller defoliation all play a role in the damage.

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Bark Beetles Infest Drought-Stressed Conifers

Posted on by akabelowsky

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

An adult bark beetle found infesting a white pine branch in 2024. / Photo Credit: Michael Hillstrom, Wisconsin DNR

Conifer mortality in southern Wisconsin has increased in 2024. Regardless of the conifer species, the common theme has been heavy infestation by bark beetles.

This increased bark beetle activity is likely linked to the 2023 drought, which lasted from May to September. Wisconsin experienced the fifth-driest May-July period on record and the fifth-driest meteorological summer (June-August) summer on record. The drought peaked during the middle of September before much-needed rain finally arrived.

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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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Basswood Trees Short On Leaves Due To Thrips

Posted on by akabelowsky

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

Photo showing Basswood leaves that have been damaged due to the feeding of introduced basswood thrips.

Basswood leaves show damage due to the feeding of introduced basswood thrips. / Photo Credit: Linda Williams, Wisconsin DNR

For the third consecutive year, damage from introduced basswood thrips (Thrips calcaratus) is significant in some areas of northeast Wisconsin, especially Forest County.

Introduced basswood thrips are tiny, invasive insects that feed inside tree buds in early spring. The feeding causes leaves to deform when they expand, looking like they suffered frost or wind damage.

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Keep An Eye Out For Beech Leaf Disease

Posted on by akabelowsky

By Kyoko Scanlon, DNR Forest Pathologist, Fitchburg;
Kyoko.Scanlon@wisconsin.gov or 608-235-7532

Forest owners and land managers should look for beech leaf disease (BLD) this summer, a destructive beech tree disease in the United States.

The disease is primarily found on American beech (Fagus grandifolia) but can also be found on ornamental species such as European, Oriental and Chinese beech (F. sylvatica, F. orientalis and F. engleriana). Although it has not yet been found in Wisconsin, recent discoveries of the disease in Michigan and other nearby states highlight the continued importance of monitoring BLD’s expansion. There is potential for BLD to move into Wisconsin as the eastern portion of the state overlaps with the native range of American beech.

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Five Years Later, Effects Of Derecho Remain

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

Over the night of July 19-20, 2019, Mother Nature carved a massive swath of destruction through northern Wisconsin.

Today, after years of hard work cleaning up after the massive derecho windstorm of ’19, local foresters, work crews and landowners have only begun to understand the breadth and depth of the damage as they process the lessons learned.

In many areas, the recovery work remains incomplete. Some of that forest damage will never receive direct attention.

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Oak Moth Outbreaks May Have Peaked In North

Posted on by akabelowsky

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

Wide-angle photo showing many oaks across northern Wisconsin with partially defoliated, thin, and yellow-tinted crowns caused by defoliation from the oak leafroller and oak leaftier.

Many oaks across northern Wisconsin displayed partially defoliated, thin, and yellow-tinted crowns caused by defoliation from the oak leafroller and oak leaftier. / Photo Credit: Paul Cigan, Wisconsin DNR

A three-year-long outbreak of oak leafroller moth and oak leaftier moth—two native, early-season oak defoliators—continued this spring in northern Wisconsin, leaving behind tens of thousands of acres of oak-dominated forest with scattered, widespread defoliation.

Partially defoliated, thin and yellow-tinted crowns were visible across portions of Barron, Rusk, Sawyer and Washburn counties, as well as areas in Florence, Forest, northern Marinette and Vilas counties.

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