Southeast WI Forest Health

Watch For Rare Fall Garlic Mustard Blooms

Posted on by akabelowsky
Photo of unusual garlic mustard plant flowering in the fall

Have you seen an unusual case of garlic mustard flowering twice in the same season? If so, please send a report to invasive.species@wisconsin.gov. / Photo Credit: Frederick Hengst, Wisconsin DNR

By Mary Bartkowiak, DNR Invasive Plant Program Coordinator, Rhinelander
Mary.Bartkowiak@wisconsin.gov or 715-493-0920

and Erika Segerson-Mueller, DNR Invasive Plant Program Specialist, Oshkosh
Erika.SegersonMueller@wisconsin.gov or 715-492-0391

Typically a biennial plant, garlic mustard blooms in the spring. So, it sounds crazy to find the plant blooming again in October.

Although garlic mustard might be taking advantage of an extended growing season, this second bloom also may be cause for concern — or, at least, careful monitoring.

Wisconsin Department of Natural Resources Tax Law Forestry Specialist Frederick Hengst discovered this “mutant” specimen in early October while on a landowner visit near Wild Rose. The plant appears to have flowered and set seed several months earlier, but then re-flowered on the same stem.

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Maple Petiole Borer Causes Leaves To Drop

Posted on by akabelowsky

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

Photo of maple leaf found on the ground with broken petiole (leafstalk).

A green maple leaf found on the ground with a broken petiole (leafstalk) due to damage by the maple petiole borer. / Photo Credit: Wisconsin DNR.

Some sugar maple trees in the northern half of Wisconsin experienced leaves dropping to the ground this spring.

These leaves were green and had no apparent areas of damage, but they covered the ground under some trees. A closer look showed these leaves had short petioles (leafstalks) that had been broken off when they fell, which indicates a tiny sawfly larva called maple petiole borer was to blame.

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Watch For Brown Spot Needle Blight

Posted on by akabelowsky
Photo showing white pine with yellowing needles.

White pine with yellowing needles; new growth is not affected. / Photo Credit: Wisconsin DNR.

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

White pine in north central Wisconsin, as well as scattered areas elsewhere in the state, have many needles that are bright yellow. Brown spot needle blight (Lecanosticta acicula, previously known as Mycosphaerella dearnessii) is the primary suspect, although samples have been sent to the Wisconsin Department of Natural Resources (DNR) Forest Health laboratory to determine if other fungal species are present.

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Severe Spruce Budworm Defoliation Hits In Northwest

Posted on by akabelowsky

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

Photo taken through magnifying lens of spruce budworm caterpillars.

Spruce budworm overwinters as tiny caterpillars (yellow arrow) that migrate to the buds before they start to swell in the spring. A magnifying lens is needed to see them at this stage. / Photo Credit: Linda Williams, Wisconsin DNR.

For the 11th consecutive year in Wisconsin, spruce budworm has caused significant defoliation on spruce, balsam fir and tamarack in some areas of the state.

This year, areas with widespread severe defoliation include Oneida and Vilas counties, with Forest, Iron, and Langlade counties also showing significant defoliation.

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Eastern Tent Caterpillar Webs Common

Posted on by akabelowsky

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

Photo of web of eastern tent caterpillars.

Eastern tent caterpillars and their webs start out small but grow quickly. Photo: Linda Williams, Wisconsin DNR.

Have you seen trees along roadsides with white webs in them? Eastern tent caterpillars (ETC) are hatching and beginning to feed on host trees, including cherry, apple and crabapple.

Landowners and homeowners may notice the white silken tents forming in branch forks. Although they form unsightly nests, ETC is a native insect, so management is not typically necessary. Even completely defoliated trees will produce new leaves within a few weeks.

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Diseases Take Aim At Spongy Moth

Posted on by akabelowsky
Photo of tree showing caterpillars killed by virus and fungus

Caterpillars killed by nucleopolyhedrosis virus (NPV) hang in an inverted “V” orientation; caterpillars killed by the fungus Entomophaga maimaiga hang vertically. Photo: Wisconsin DNR.

By Bill McNee, DNR Forest Health Specialist, Oshkosh
bill.mcnee@wisconsin.gov or 920-360-0942

With this spring’s dry weather in Wisconsin came predictions of the largest spongy moth population in years.

When spongy moth populations are high, we often see heavy mortality of the larger caterpillars due to two pathogens. Heavy caterpillar mortality will reduce the severity of the following year’s outbreak and often causes a population crash during the current year. If a heavy die-off of caterpillars is observed, please let your local DNR Forest Health Specialist know about it.

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Spongy Moth Focus Of Video, Webcast

Posted on by akabelowsky

Art Kabelowsky, DNR Forest Health outreach and communications specialist
Arthur.Kabelowsky@wisconsin.gov or 608-335-0167

Add “YouTube Influencer” to the long list of career accomplishments of Andrea Diss-Torrance, Ph.D.

With the spongy moth caterpillar population on the rise in many areas of Wisconsin this season, the Wisconsin Department of Natural Resources stepped into action last month.

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Spongy Moth Forecast Caution Issued

Posted on by akabelowsky

By Bill McNee, Forest Health Specialist, Oshkosh
bill.mcnee@wisconsin.gov or 920-360-0942

Photo of mature spongy moth caterpillar

Mature spongy moth caterpillar on a leaf. Photo: Bill McNee, Wisconsin DNR

Wisconsin Department of Natural Resources Forest Health staff are cautioning Wisconsin residents that the next two months could bring the worst spongy moth outbreak in more than a decade.

The caterpillars of this invasive insect prefer to feed on oak, birch, crabapple, aspen and willow leaves, but will also feed on many other tree and shrub species.

Southern Wisconsin and parts of the north are already in a high-population outbreak that is predicted to continue and spread. Populations have remained high due to a low incidence of caterpillar-killing diseases last summer. In addition, weather conditions in 2023 are favorable for the caterpillars and unfavorable for Entomophaga maimaiga, a fungus that kills spongy moth caterpillars.

Property owners are encouraged to examine their trees and take action.  Specifically:

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Aerial Spraying Set For Four State Sites

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By Bill McNee, Forest Health Specialist, Oshkosh, Bill.Mcnee@wisconsin.gov or 920-360-0942

Spray aircraft used in spongy moth control

Spray aircraft used in spongy moth control. Photo: Bill McNee

At a suitable time between early May and early June, an airplane will spray parts of four DNR properties to reduce the population of spongy moth caterpillars (formerly known as gypsy moth). Treatment dates will depend on weather conditions and caterpillar development.

This year’s high populations threaten to strip trees of their leaves and possibly kill high-value trees at these properties.

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Protect Oak Trees From Oak Wilt By Pruning After July, Not Before

Posted on by eleanorvoigt

By Don Kissinger, DNR Urban Forester, 715-348-5746 or Don.Kissinger@wisconsin.gov; Paul Cigan, DNR Forest Health Specialist, 715-416-4920 or Paul.Cigan@wisconsin.gov

The Wisconsin Department of Natural Resources (DNR) urban and forest health specialists recommend not pruning or cutting oaks from April through July to protect oak trees from the often fatal oak wilt disease.

The spring season often draws property owners outdoors to soak up rays of long-awaited sunlight, breathe in some fresh air and begin seasonal yard maintenance and cleanup projects. While spring is a time to dust off yard tools like rakes, shovels and weed clippers, when it comes to the health of oak trees, keeping those chainsaws and trimming tools a safe distance away will go a long way to ensure that your trees stay healthy for many more spring seasons to come.

Sap-feeding beetle on a diseased oak tree in Sawyer County.

Sap-feeding beetle on a diseased oak tree in Sawyer County.

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