Care for your woods

Just Say ‘No’ To Knotweeds

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Photo showing a worker logging a large roadside infestation of knotweed.

Species in the knotweed complex grow very quickly, causing large infestations on roadsides like this one. / Photo Credit: Randy Westbrooks, Invasive Plant Control, Inc., Bugwood.org

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

As you work on your New Year’s resolutions this year, you might want to add “don’t plant invasive species” to your list. Too wide-ranging? Try narrowing the goal to a species-specific suggestion: “Just say ‘no’ to knotweeds.”

Sometimes referred to as “the knotweed complex,” Wisconsin has three regulated species of knotweed: Japanese knotweed, giant knotweed and a hybridization known as Bohemian knotweed. Each has been found in the state.

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Green Light On For Oak Tree Work

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Photo of fallen leaves from a red oak that show discoloration, an indication that the tree is infected with oak wilt.

Discolored fallen leaves from a red oak tree indicate that the tree is infected with oak wilt. / Photo Credit: Wisconsin DNR

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

With the weather taking its time to turn wintry, it’s a good time to remind landowners and work crews that now through the end of March is an ideal time to perform pruning, trimming and brush removal on and near oak trees.

This is a low-risk period for the trees to be infected with oak wilt, a fungal disease spread by beetles. When a red oak is infected with oak wilt, it will die that year. The disease also stresses white oaks, often proving fatal.

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Fight Invasives As Part Of A CISMA

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

Photo of a goat grazing during a demonstration held by the Monroe County Invasive Species Working Group

A field day in August 2023, hosted by Monroe County Invasive Species Working Group, featured a live goat grazing demonstration among presentations that included invasive plant identification tips, funding opportunities and management techniques. / Photo Credit: Wisconsin DNR

If you’ve been fighting invasive plants in your woodlands, you may have wondered if there were any groups in your area to support weed management. The short answer? Probably!

Wisconsin currently has 14 different Cooperative Invasive Species Management Areas, or CISMAs. These regional county groups bring together community members to work on various invasive species-related projects ranging from fieldwork outings to controlling and monitoring invasive plant occurrences to education and outreach events so more local citizens can learn about and get involved with invasive plant management.

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Winter Work: Invasive Honeysuckle Treatment

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Cross-section photo of the brown and hollow pith of the invasive honeysuckle plant.

The pith of invasive honeysuckle, seen here, is brown and hollow. / Photo Credit: Chris Evans, University of Illinois, Bugwood.org

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

They may have sweet-sounding names, but Eurasian bush honeysuckles (Lonicera spp.) can bring a bitter taste to your mouth if found in your woodlands.

Originating as horticultural plantings, this group of upright woody shrubs is now widespread in Wisconsin and the upper Midwest.

Invasive honeysuckle shrubs are among the earliest plants to leaf out in the spring and the last to lose their leaves in the fall. This extended growing season allows them to outcompete other plants for nutrients and sunlight, casting dense shade on the forest floor.

Native honeysuckles are also present in Wisconsin. Several identifying characteristics can help you determine if your honeysuckle is a native species or one of the invasive varieties. When in bloom, the flowers of invasive Bell’s, Morrow’s and Tartarian honeysuckles are easily distinguished. Without the blooms, the easiest methods to determine non-native honeysuckle from the native plant include looking for shaggy, peeling gray-brown bark and checking the pith.

The pith (inner tissue of the branches and stems) can be observed by breaking off an older branch. If the pith appears white, the shrub is native honeysuckle. If the pith is brown and hollow, it is likely one of the invasive bush versions.

Winter is a great time to treat invasive honeysuckle shrubs on your property since most other plants have gone dormant for the season. Winter herbicide applications are highly successful on freshly cut stumps, provided snow does not cover the cut surface. Basal bark applications may also be used on snow-free surfaces.

Stump cutting should be followed by herbicide treatments, as vigorous resprouting may occur from shrubs cut in winter but not treated with herbicide. Learn more about invasive honeysuckles and how to manage them on the Bush honeysuckles fact sheet from Renz Weed Science at the University of Wisconsin-Extension.

Make Your 2024 Spongy Moth Treatment Plans Early

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Photo of a finger pointing to a tan-colored spongy moth egg mass on a tree.

A finger points to a tan-colored spongy moth egg mass on a tree. / Photo Credit: Bill McNee, Wisconsin DNR

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

If the 2024 spring and summer weather conditions are favorable for the spongy moth (Lymantria dispar) population, the current outbreak will continue and spread to other parts of Wisconsin. Property owners are encouraged to examine susceptible host trees (including oak, birch, crabapple, aspen and willow) and make plans to manage them.

In summer 2023, Wisconsin saw a record amount of defoliation. State agencies received many calls from property owners urgently seeking a tree care business to control a large caterpillar infestation.

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Harvest Timing Affected By Spongy Moth

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Photo showing numerous spongy moth egg masses on an oak tree in Walworth County, Wisconsin

Numerous spongy moth egg masses on an oak tree in Walworth County. / Photo Credit: Bill McNee, Wisconsin DNR

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

Forest managers planning silvicultural treatments in stands susceptible to spongy moth (Lymantria dispar) – such as those containing many host species, including oak, birch, aspen and basswood – are encouraged to conduct annual egg mass surveys before treatment.

Surveys make it possible to predict if heavy defoliation is likely. If more than 30 egg masses are found in a sample area – a circle with a 37-foot diameter – then heavy defoliation is expected in the spring, and management activities should be altered or delayed until an outbreak has ended. Continue reading “Harvest Timing Affected By Spongy Moth” →

Oak Wilt Confirmed In Ashland County

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Map showing Wisconsin counties in which oak wilt has been detected.

With the addition of Ashland County, oak wilt has now been detected in 66 of Wisconsin’s 72 counties. / Map Credit: Wisconsin DNR.

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

Oak wilt, a deadly disease of oaks, has been found for the first time in Ashland County.

The Wisconsin Department of Natural Resources (DNR) confirmed the find in wood samples from a red oak tree in the town of Gordon.

“There is always risk of oak wilt spread into new and relatively uninfested areas in northern Wisconsin, such as Ashland County, so it’s always best to practice oak wilt prevention wherever possible to significantly reduce that risk,” said Paul Cigan, a DNR forest health specialist based in Hayward.

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Don’t Let Tree Trouble Hitch A Ride On Firewood

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Photo of spongy moth egg masses attached to a piece of firewood

A pair of spongy moth egg masses attached to a piece of firewood. Moving this firewood to another site could put trees at that site at risk in the spring. / Photo Credit: Wisconsin DNR

By Art Kabelowsky, DNR Forest Health Outreach/Communications
Arthur.Kabelowsky@wisconsin.gov or 608-335-0167

Are you generally hesitant to give hitchhikers a free ride?

October was National Firewood Awareness Month, and even though November has arrived, the Wisconsin Department of Natural Resources (DNR) continues to urge residents and visitors to follow the same line of thinking when it comes to moving firewood.

That’s because tree-killing hitchhikers often lurk on or in firewood — including spongy moth, emerald ash borer, the fungus that causes oak wilt and other invasive insects and fungi. When untreated, infested firewood is transported away from where the tree died, those pests and fungi can later emerge to attack trees at the new site. This can happen whether that new location is in the next town or hundreds of miles away.

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Oak Mortality Increases In 2023

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Photo of a bur oak tree more than 100 years old showing canopy dieback and epicormic branching due to twolined chestnut borer

A bur oak more than 100 years old exhibits canopy dieback and epicormic branching caused by twolined chestnut borer. / Photo Credit: Wisconsin DNR

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

White, red and bur oaks have been experiencing increased mortality in Wisconsin and neighboring states over the last few years.

The causes of mortality are varied, but two-lined chestnut borer (TLCB) is the most common culprit. Wisconsin has switched from a period of historically wet years (2017-2020) to drought conditions that have become more severe each year (2021-2023). Add in frost damage, storm damage, increased growing season length and aging forests and the environmental recipe exists for stressed oaks that are more susceptible to attack by insects and diseases.

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Watch For Rare Fall Garlic Mustard Blooms

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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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