Care for your woods

Oak Wilt Confirmed In Ashland County

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 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

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 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

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

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

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 / Photo Credit: Frederick Hengst, Wisconsin DNR

By Mary Bartkowiak, DNR Invasive Plant Program Coordinator, Rhinelander or 715-493-0920

and Erika Segerson-Mueller, DNR Invasive Plant Program Specialist, Oshkosh 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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Article Sets Record Straight On Value Of EAB Management

Photo of an adult emerald ash borer beetle on a tree trunk

An adult emerald ash borer beetle on a tree trunk. The invasive insect is expected to eventually kill 99 percent of ash trees in Wisconsin. / Photo Credit: Bill McNee, Wisconsin DNR

By Art Kabelowsky, DNR Forest Health Outreach/Communications or 608-335-0167

Entomology Today magazine has published an article debunking common misconceptions about management of emerald ash borer (EAB). The information in the article can be helpful to communities and landowners deciding whether to invest in treatment to preserve ash trees.

The article focuses on treatments for high-value trees, not those in woodlands. The advice in the summary is clear for communities, property managers of high-use recreational lands and homeowners with ash near residences:

“Allowing nature to take its course is a budget-busting option.”

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Another Ash Pest Found In Northern Wisconsin

Close-up photo of an adult cottony ash psyllid.

A close-up photo of an adult cottony ash psyllid feeding on an ash leaf. / Photo Credit: Steve Garske, Great Lakes Indian Fish and Wildlife Commission

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

As if black ash trees don’t have enough problems with emerald ash borer (EAB), another ash pest recently was found at several locations in northern Wisconsin.

In June, Great Lakes Indian Fish and Wildlife Commission (GLIFWC) staff noticed black ash with leaf curling and puckering, early leaf drop and dieback at one of their Climate Change Program’s long-term phenology study sites.

After working with DNR Forest Health staff to narrow down the possibilities, insect samples were collected and sent to P.J. Liesch, director of the University of Wisconsin-Madison Insect Diagnostic Laboratory, for official identification. He identified them as cottony ash psyllid.

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DNR Debuts Video On Scraping Spongy Moth Egg Masses

Photo of Wisconsin DNR's Andrea Diss-Torrance scraping a spongy moth egg mass off a tree.

Wisconsin DNR invasive forest insects program coordinator Andrea Diss-Torrance demonstrates scraping a spongy moth egg mass off a tree while making a video on the subject for the DNR. / Photo Credit: Wisconsin DNR

By Art Kabelowsky, DNR Forestry Outreach/Communications Specialist or 608-335-0167

The fall and winter months present a perfect opportunity to protect trees by searching out and removing spongy moth egg masses.

The invasive insects currently exist only as tiny eggs, camped out in egg masses that can be found in places such as tree trunks and branches, under park picnic benches and swing sets, and under the awnings of buildings.

And now, the Wisconsin Department of Natural Resources (DNR) has debuted a short video showing exactly how to easily and safely remove egg masses to reduce next spring’s population of hungry spongy moth caterpillars.

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Fall: Time To Treat Invasive Plants

By Erika Segerson-Mueller, DNR Invasive Plant Program Specialist, Oshkosh Service Center; or 715-492-0391

As we move into cooler temperatures, many plants and trees are changing in leaf color and even beginning to drop their leaves. The Wisconsin Department of Natural Resources (DNR) reminds the public that fall is not only a great time to enjoy the changing hues in the woods, but it also presents a good opportunity to spot the invasive plants persisting among them.

As you walk through your woods this month, look for leaves that stay green into late fall, even after all other trees have lost their leaves. These are likely signs of an invasive plant species.
Invasive plants can hold onto their leaves much longer than native plants, taking advantage of late fall sunshine and ensuring they continue to grow and gain ground in the forest after many other plants have already died out or gone dormant for the winter.

Late autumn and even early winter are great times to identify and treat invasive plants. They are easy to see in a sea of downed leaves and dead plants. The absence of living native plants means that treating invasives with chemical herbicides will cause much less collateral damage.

Fall treatment is ideal for woody invasives, as trees and shrubs are busy directing resources to their roots to store them for overwintering, so the natural flow carries the herbicide along to the roots. Spring treatments are often ineffective because the opposite is true: plants are continually pushing resources up and out toward new buds.

When a control method like cut-and-swipe (a common treatment for buckthorn that involves snipping off stems and using a dabber to apply herbicide directly to the cut) is used in spring, it is often ineffective as the herbicide is immediately pushed out of the plant. In fall and winter, the flow of resources changes, making treatment much more effective.

Common invasive plants that can be treated in fall include garlic mustard, non-native honeysuckles and common and glossy buckthorns. Here are some basic identification characteristics and methods of treatment:

Garlic Mustard

Photo of rosettes on a garlic mustard plant. / Photo Credit: Wisconsin DNR

Rosettes on a garlic mustard plant. / Photo Credit: Wisconsin DNR

Though not a woody plant, the basal rosettes (a cluster of leaves at ground level) remain green through the fall and winter and are easy to spot. Garlic mustard looks somewhat like wild ginger or violets due to its kidney-bean shaped leaves. To check, crush a leaf – the leaves of garlic mustard should have a garlic smell when crushed.

If only a few plants are present, they can be hand-pulled and should be destroyed by burning or sending them to a landfill in bags clearly labeled as “Invasive Plants – Approved by Wisconsin DNR for Landfill.” For larger infestations, plants may be cut or torched, or herbicide may be used as recommended in the Control Method section of the Garlic Mustard Fact Sheet.

Non-Native Honeysuckles

Photo of an invasive honeysuckle plant.

Photo of a honeysuckle plant. / Photo Credit: Wisconsin DNR

Non-native honeysuckles can hold their leaves well into winter. They often have a thick canopy of leaves that shades out native plants. While other plants are bare and the honeysuckle still has that thick canopy, it’s a great time to attack and treat it.

There are several types of invasive honeysuckles in Wisconsin. Learn more about each variety as well as control methods on the Management of Bush Honeysuckles fact sheet from the University of Wisconsin-Extension.

Common And Glossy Buckthorn

Photo of a glossy buckthorn shrub covered in berries

A glossy buckthorn shrub covered in berries. Control berry-producing plants first to prevent further spreading. / Photo Credit: Wisconsin DNR.

A common sight in Wisconsin forests, common and glossy buckthorn is also best treated in late fall and early winter. Buckthorn is a multi-stemmed large shrub or small tree that can form an impenetrable understory layer, displacing native vegetation.

Small buckthorn seedlings can be removed by hand. Larger plants should be cut or girdled at the base. Buckthorn can easily re-sprout from cut stumps, so herbicide treatments are often best. Find more information on control methods on the Buckthorns Management Fact sheet.

After treating any invasive plants in the fall, make sure to follow up in spring to check for new growth and seedlings. Controlling invasive plant species almost always requires multiple treatments and monitoring over several seasons.

Tree City USA Application Portal Now Open

The application portal for Tree City USA is now open and available. Applications are due Dec. 31.

You will notice some changes to the recognition portal this year. These instructions will help you log in for the first time.

We hope you join us again this year in continuing our strong commitment to growing and maintaining a healthy tree canopy across Wisconsin. If you’re new to Tree City USA, you can learn more about the program on the Arbor Day Foundation’s website and from your DNR Urban Forestry Coordinator.

If you’ve been a Tree City USA for at least one year, you may want to see whether you’re eligible for a Growth Award. The Growth Award is presented by the Arbor Day Foundation to participating Tree City USA communities that demonstrate higher levels of tree care and community engagement during the calendar year. Communities need to earn at least ten points in any of the following five categories: Building the Team, Measuring Trees & Forests, Planning the Work, Performing the Work and The Community Framework. Review the point system to see if you’re eligible this year and talk to your Urban Forestry Coordinator if you have any questions.

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Avoid Invasives During Fall Recreation

Photo of firewood self-service stand at a Wisconsin state park

Don’t move firewood! Many State Parks and Forests stock firewood right at the campground entrances. Use these stands or other local sources that are no more than 10 miles from your destination to avoid spreading invasive species. / Photo Credit: Wisconsin DNR

Erika Segerson-Mueller, DNR Invasive Plant Program Specialist, Oshkosh Service Center; or 715-492-0391

Whether you prefer to enjoy Wisconsin’s beautiful fall weather on a hike, bike, ATV/UTV or on the water, the Wisconsin Department of Natural Resources (DNR) urges those enjoying the outdoors to take a few precautions to avoid bringing invasive plant species along for the ride.

The Wisconsin Council on Forestry has created a set of guidelines titled “Invasive Species Best Management Practices for Outdoor Recreation.” These voluntary guidelines include steps recommended for individuals to minimize the inadvertent spread of invasive species.

Here are a few universal Best Management Practices (BMPs) for outdoor recreation, along with a few examples of these practices in action.

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