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Jack Pine Budworm Outbreak Subsides

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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

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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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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.

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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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Forest Health Public Appearance Set

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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.

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Which Thistle Is This Thistle?

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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

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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

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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

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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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