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Oak Decline Continues In Southern Wisconsin

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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.

Continue reading “Oak Decline Continues In Southern Wisconsin” →

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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Forest Health Public Appearance Set

Posted on by akabelowsky

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

Wisconsin Department of Natural Resources Forest Health team leader Becky Gray will discuss invasives during a presentation to the Southeastern Wisconsin Invasive Species Consortium, set for Wednesday, Nov. 6, at Havenwoods State Forest in Milwaukee. / Photo Credit: Art Kabelowsky, Wisconsin DNR

Forest Health team leader Becky Gray has planned an appearance at a public meeting of the Southeastern Wisconsin Invasive Species Consortium (SEWISC). She’ll give a presentation covering invasives on a statewide level.

The event will take place from 1 to 4 p.m. Wednesday, Nov. 6, at Havenwoods State Forest, 6141 N. Hopkins St., Milwaukee, WI. More information is available on the SEWISC website.

Williams to appear at WWOA event: Linda Williams will take part in a Field Day event to discuss oak and pine issues during the four-day Wisconsin Woodland Owners Association meeting, set for Sept. 26-29 in Marshfield and Stevens Point. Four tours will take place Sept. 27; the Field Day will take place Sept. 29 at Pine Bluff Tree Farm in Stevens Point.

The event is open to the public. For more information, visit the event’s website or call 715-346-4798.

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.

Continue reading “Squirrels Love Acorn Pip Galls And Weevils” →

Which Thistle Is This Thistle?

Posted on by akabelowsky

By Erika Segerson-Mueller, DNR Invasive Plant Program Specialist, Oshkosh Service Center;
erika.segersonmueller@wisconsin.gov or 715-492-0391

With 10 thistle species present in Wisconsin, it can be tricky to determine which thistle is which. You may be tempted to control every thistle you see, assuming all types are invasive. But Wisconsin also has native thistles that provide valuable habitat and food for small birds and butterflies.

Thistles are either biennials (following a two-year life cycle) or perennials (regrowing every spring). They have lobed, spiny leaves and sometimes spiny stems. Thistles have composite flowers, with each flowerhead being composed of many tiny flowers, or florets.

Read on a for an overview of invasive thistles found in Wisconsin so you can stop wondering: Which thistle is this thistle? Continue reading “Which Thistle Is This Thistle?” →

CISMA Events For August, September

Posted on by akabelowsky

By Erika Segerson-Mueller, DNR Invasive Plant Program Specialist, Oshkosh Service Center;
erika.segersonmueller@wisconsin.gov or 715-492-0391

A chart showing Wisconsin's different Cooperative Invasive Species Management Areas boundaries.When it comes to fighting invasive plants, Wisconsin’s CISMAs (Cooperative Invasive Species Management Areas) are often the first line of defense (and offense). These regional groups provide a localized resource for landowners looking for invasive plant education, identification support and assistance with controlling invasives on their properties. Continue reading “CISMA Events For August, September” →

New Invasive Pest Discovered In Wisconsin

Posted on by akabelowsky

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

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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.

Continue reading “Dropping Leaves May Indicate Oak Wilt” →