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Green Light On For Oak Tree Work

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

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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New-And-Improved USDA Plant Hardiness Zone Map

The USDA Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which perennial plants are most likely to thrive in a given location. The map is based on the average annual extreme minimum winter temperature, displayed as 10-degree Fahrenheit zones and 5-degree Fahrenheit half zones.

WI USDA Plant Zone MapThirty years of data was reviewed by a group of horticultural, botanical and climatological experts for the latest USDA Plant Hardiness Zone Map revision. This was determined to be the best balance between the fluctuations of year-to-year weather variation and the concept that, during their lifetimes, perennial plants mostly experience what is termed “weather” rather than “climate.”  A complex algorithm was used for this edition of the Plant Hardiness Zone Map to enable more accurate interpolation between weather reporting stations. This method accounts for factors such as elevation change and proximity to bodies of water, making mapping zones more accurate. Continue reading “New-And-Improved USDA Plant Hardiness Zone Map”

Keep Invasive Plants Out Of Spring Garden Plans

Photo of the invasive plant Japanese barberry

Originally planted as a garden ornamental, Japanese barberry can quickly escape cultivation and invade Wisconsin’s woodlands. / Photo Credit: Wisconsin DNR

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

While winter is just beginning to creep in on Wisconsin, many gardeners are already thinking ahead to the next spring planting season. While dreaming of spring blooms and designing your next garden or landscape layout, consider invasive plants that may try to weed their way into your plans.

Many invasive plants that are problematic for Wisconsin forests started as garden ornamentals. Although Wisconsin regulates 145 plants under the invasive species rule NR 40 prohibiting their sale, it’s essential to check your selections before purchasing and choose native plants when possible.

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Video Reminds Public Of Impact Of Heterobasidion Root Disease

Photo frame from a DNR-produced video on heterobasidion root disease

A Wisconsin Department of Natural Resources video on Heterobasidion root disease shows ways to identify the disease and presents best management practices. / Photo Credit: Wisconsin DNR

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

Now is an excellent time to look for symptoms of Heterobasidion root disease (HRD), a fungal disease that attacks and kills pine and spruce trees. The disease is present in 30 of Wisconsin’s 72 counties.

The Wisconsin Department of Natural Resources has produced a video, a fact sheet and a booklet of silvicultural guidelines to manage the disease. The video and other links are on the DNR’s Forest Health webpage for HRD.

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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
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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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 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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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
Arthur.Kabelowsky@wisconsin.gov 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
Linda.Williams@wisconsin.gov 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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Fall: Time To Treat Invasive Plants

By Erika Segerson-Mueller, DNR Invasive Plant Program Specialist, Oshkosh Service Center;
Erika.Segersonmueller@wisconsin.gov 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.