Ambrosia Beetles Attack Sugar Maple Regeneration

By Kyoko Scanlon, DNR Forest Pathologist, Fitchburg,

This summer, the Forest Health Lab received sugar maple seedlings with brownish yellow leaves, which were sent by a Waukesha County landowner who observed many understory sugar maple seedlings and saplings quickly turning brown throughout the summer. This mortality continued until the end of September. The landowner wanted to know why these plants were dead and dying.

Seeding with yellow leaves surrounded by green seedlings.

Affected seedlings exhibit yellow and brown leaves. Photo: Wisconsin DNR

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Twolined Chestnut Borer Attacks On The Rise

By Paul Cigan, DNR Forest Health Specialist, Hayward, or 715-416-4920

Twolined chestnut borer (TLCB) attacks on oak trees have increased in numerous Wisconsin counties, with decline and associated mortality in the last two growing seasons, most noticeably since August.

Symptoms of infestation by this native beetle are initially seen in mid-July on the outer portions of branches in the upper crown. Leaves begin to fade from green to yellow to red. Within a matter of weeks, they turn brown and remain on the branches for weeks to months. Their foliage may also appear sparse or completely bare (Fig. 1).

Trees with twolined chestnut borer symptoms

Figure 1. Northern red oaks with symptoms of twolined chestnut borer, ranging from crown thinning and leaf chlorosis like the tree on the left (early stage) to dead top branches like the tree on the right (intermediate stage). Photo: Wisconsin DNR

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Moving Firewood Can Spread Invasive Species

An image of an insect walking away from burning firewood in a forest with the caption, “Buy it where you burn it.”

Don’t Move Firewood, The Nature Conservancy

October is Firewood Month! Help prevent the spread of invasive insects and diseases by buying firewood where you burn it.

Firewood Scout can help you find local firewood for sale.

See the DNR website for more information on invasive species and forest health. Continue reading “Moving Firewood Can Spread Invasive Species”

Avoid Ash Trees When Placing Deer Stands

By Bill McNee, DNR Forest Health Specialist, or 920-360-0942

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

Hunter in trees

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

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Grant Funds Available For Community EAB Management

By: Abigail Krause, DNR Urban Forestry Coordinator

As more detections of emerald ash borer (EAB) are confirmed in Wisconsin’s northern counties, many communities are just starting to address the management consequences that others having been dealing with for more than a decade. Members of the communities in which you live and work may vaguely know of you as “that one person that knows things about trees.” As such you may get asked: are there any cost-share funds or programs out there to help communities deal with EAB?

The answer is yes! Urban Forestry’s grants can be utilized for EAB related projects. Extra great news: urban forestry regular and startup grants are accepting applications until Monday, Oct. 3.

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Look For Spongy Moth Egg Masses – Larger Outbreak Possible in 2023

By: Bill McNee, DNR Forest Health Specialist, Oshkosh or 920-360-0942

Three tan-colored spongy moth egg masses on a single tree branch in Walworth County.

Three spongy moth egg masses on a branch in Walworth County. Photo Credit: Bill McNee, Wisconsin DNR

Now that spongy moth* (formerly known as gypsy moth) egg laying is complete for 2022, it’s a good time to look for and dispose of egg masses produced by adult moths over the past two months.

Spongy moth egg masses are tan-colored lumps about the size of a nickel or quarter, and are found on trees, buildings and other outdoor objects. They may also be found in protected places such as firewood piles and birdhouses. Newly produced egg masses will feel firm and appear darker in color than older egg masses, which appear faded, feel spongy and do not contain viable eggs. The current-year egg masses will not hatch until next spring.

In 2022, Wisconsin’s spongy moth population grew for a third consecutive summer due to favorable weather conditions and limited caterpillar mortality from diseases. The outbreak was most dramatic in opposite ends of the state. In southern and southeast Wisconsin, several thousand oak-dominated acres were heavily defoliated and very large numbers of property owner reports were received by DNR staff. In Bayfield County, about 80,000 acres of rural defoliation was reported from aspen-dominated forests. Smaller patches of defoliation were also reported from several other counties. Continue reading “Look For Spongy Moth Egg Masses – Larger Outbreak Possible in 2023”

Red Oak Irony

By Paul Cigan, DNR Forest Health Specialist, Hayward, or 715-416-4920

Red oak trees in many areas of northern Wisconsin are aptly fitting their name as many crowns exhibit a red hue this summer.

A red oak tree with a red and green leaves.

Red oaks are producing a second flush of leaves following oak leafroller defoliation in spring, resulting in trees with red-looking crowns. Photo: Wisconsin DNR

Widespread defoliation by oak leafrollers in May and June has led many oaks to generate a second set of leaves after being stripped. New expanding leaves often display a prominent red color that gives the tree crown a stark reddish appearance from afar.

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Hairy Spring Caterpillars – Which One Do You Have?

By Linda Williams, DNR Forest Health Specialist, Woodruff or 920-360-0665

Wisconsin has a few leaf-eating caterpillar species that are out early in the spring. Forest tent caterpillars, eastern tent caterpillars and spongy moth caterpillars cause varying levels of tree damage and are often mistaken for one another.

A group of many forest tent caterpillars on the bark of a tree.

Forest tent caterpillars congregating on the trunk of a tree. Photo: Wisconsin DNR

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Basswood Thrips: Tiny Terrors Of Basswood Leaves

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

Introduced basswood thrips are tiny, invasive insects that feed inside tree buds in early spring. Leaves are then deformed when they expand and can look like frost or wind has damaged them.

A long and thin introduced basswood thrips rests on the underside of a small green leaf.

An adult introduced basswood thrips on the underside of an emerging basswood leaf. This photo is enlarged under a microscope. To the naked eye, they appear as tiny black specks on the underside of the leaf. Photo: Wisconsin DNR

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