Pest

Check Conifers For Invasive Adelgids

Posted on by akabelowsky
Photo showing white, cottony hemlock woolly adelgid egg sacs on a hemlock branch.

White, cottony hemlock woolly adelgid egg sacs on a hemlock branch. / Photo Credit: Bill McNee, Wisconsin DNR

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

Hemlock woolly adelgid (HWA) and balsam woolly adelgid (BWA) are invasive, aphid-like insects that cause tree mortality in North America. Neither has been found in Wisconsin so far, but they are likely to arrive at some point, as they have been confirmed in Michigan.

HWA (Adelges tsugae) is an invasive, sucking insect pest of hemlock trees. The white, cottony egg sacs of HWA can be seen on the undersides of hemlock branches at the base of needles year-round. HWA saliva enters the tree while feeding. The saliva is toxic and causes needle drop and twig dieback, progressing to tree mortality in 4-10 years.

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Winter Squirrel Damage Killing Maple Branches

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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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Hemlock Monitored After 2023 Defoliation

Posted on by akabelowsky

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

Photo showing that hemlock crowns remained thin this summer at a Vilas County plot that saw defoliation by spruce budworm in 2023.

Hemlock crowns remained thin this summer at a Vilas County plot that saw defoliation by spruce budworm in 2023. / Photo Credit: Linda Williams, Wisconsin DNR

Spruce budworm was observed defoliating a stand of hemlock trees in Vilas County in 2023. This stand was revisited in 2024 and although defoliation was only light this year, significant thinning in the tops of hemlocks was noted.

Hemlock is not a preferred host for spruce budworm, and the defoliation in 2023 was due to an extremely high population of spruce budworm in that area.

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Bark Beetles Infest Drought-Stressed Conifers

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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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Squirrels Love Acorn Pip Galls And Weevils

Posted on by akabelowsky

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

Closeup photo of six acorns. One still has pip galls; the others have had their pip galls eaten by squirrels.

The acorn farthest on the right has pip galls. Squirrels ate the pip galls from the other acorns. / Photo Credit: Linda Williams, Wisconsin DNR

Several areas in northern Wisconsin have reported significant acorn drop. In almost all cases, these acorns have been damaged by either pip galls or acorn weevils.

Squirrels enjoy feeding on pip galls and will pluck those acorns off the tree, rip off the cap, eat the pip gall and drop the rest of the acorn to the ground. Squirrels will also seek out acorns infested by acorn weevils. They will open those acorns, eat the larvae and then drop the rest of the acorn to the ground.

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New Invasive Pest Discovered In Wisconsin

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

A closeup of an elm zigzag sawfly caterpillar consuming a leaf. The invasive insect, new to Wisconsin, was found on an elm tree near the Wisconsin Department of Natural Resources office in Oshkosh on July 16, 2024.

A closeup of an elm zigzag sawfly caterpillar consuming a leaf. The invasive insect, new to Wisconsin, was found on an elm tree near the Wisconsin Department of Natural Resources office in Oshkosh on July 16, 2024. / Photo Credit: Bill McNee, Wisconsin DNR

The invasive insect elm zigzag sawfly (Aproceros leucopada) has been detected in Wisconsin for the first time.

Following the initial Wisconsin discovery in Portage County on July 4. Through Aug. 12, the pest has since been detected in 17 Wisconsin counties. Continue reading “New Invasive Pest Discovered In Wisconsin” →

Larch Casebearer Damage Spotted In North

Posted on by akabelowsky

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

Photo showing a tamarack tree branch with severe needle mining from larch casebearer. / Photo Credit: Paul Cigan, Wisconsin DNR

A tamarack branch shows severe needle mining from larch casebearer. / Photo Credit: Paul Cigan, Wisconsin DNR

Larch casebearer has caused localized heavy defoliation in some tamarack swamps in central Burnett County this spring, causing tamarack to stand out with a stark appearance of bright-brown foliage by mid-June.

Larvae of this exotic moth damage tamarack needles by “mining” the inner needle tissue. Heavily damaged tamarack progress in color from pale green to yellow and eventually turn a bright, reddish brown as needles dry out and die.

 

 

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Spruce Budworm Defoliation Continues

Posted on by akabelowsky

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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