Woodland owners

Make Your 2024 Spongy Moth Treatment Plans Early

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

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”

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.

Look For Spongy Moss Egg Masses

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

Photo of spongy moth egg masses on a tree.

Three spongy moth egg masses are found on a tree branch at Kettle Moraine State Forest Southern Unit in Walworth County. / Photo Credit: Bill McNee, Wisconsin DNR

Now that spongy moth egg laying is complete for 2023, it’s a good time to look for and dispose of the 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 can be found on trees, buildings and other outdoor objects. They may also be found in protected places such as firewood piles and birdhouses.

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High Beech Scale Moving Beyond Door County

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

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

Photos of white 'wool' coating on trees with beech scale.

Examples of white “wool” coating on trees heavily infested with beech scale at Kohler-Andrae State Park (left) and in the Town of Beecher in Marinette County (right). / Photo Credit: Bill McNee (left) and Linda Williams (right), Wisconsin DNR.

Fourteen years after first detecting beech scale (Cryptococcus fagisuga, a non-native insect) in Door County, sites with high populations of beech scale have been found in additional counties. Beech scale is believed to have spread through the range of American beech in Wisconsin’s eastern counties, but until now has only been seen at low levels outside of Door County.

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White Pine Weevil Damage And Management Options

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

Photo of a white pine tree showing weevil damage.

A dead terminal leader, resulting from an attack by white pine weevil. Photo: Linda Williams, Wisconsin DNR.

White pine weevil (Pissodes strobi) is a native insect that can kill the terminal leader of white pine, jack pine and spruce. Wisconsinites often refer to this insect as Tip Weevil.

The insects prefer to attack stout terminal leaders. When the terminal leader dies, lateral branches grow upward and compete to take over apical dominance. This can leave a noticeable crook for decades. If two or more lateral branches take over, forking can occur. New terminal leaders may be attacked in subsequent years, causing more crook or forking.

Spruce and jack pine tend to recover better from weevil damage than white pine because the lateral branch that takes over apical dominance often creates a less prominent crook.

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Is it Invasive Giant Hogweed?

Erika Segerson-Mueller, DNR Forest Health invasive plants program specialist, Oshkosh
Erika.SegersonMueller@wisconsin.gov or 715-492-0391

Photo of umbel of a giant hogweed plant.

Umbel of a giant hogweed plant. This invasive plant can grow stems 2-4 inches in diameter and can grow as tall as 15 feet. Photo: USDA APHIS PPQ, Oxford, North Carolina; Bugwood.org

This time of year, calls start rolling in about potential sightings of the invasive plant giant hogweed (Heracleum mantegazzianum). Although occurrences of the plant remain rare in Wisconsin, from late May through early July giant hogweed is often confused with a native plant, cow parsnip (Heracleum maximum).

Both are large plants with similar habitat preferences. They prefer shady areas and are often found along stream banks, roadsides and ditches. Giant hogweed is a prohibited species under Wisconsin’s Invasive Species Rule NR40. Its fast growth rate crowds out native vegetation and erodes soil, and skin contact can potentially cause irritation.

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Eastern Tent Caterpillar Webs Common

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

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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