Pest

Emerald Ash Borer Detected In Rusk County

Posted on by akabelowsky

By Paul Cigan, DNR Forest Health Specialist, Hayward
Paul.Cigan@wisconsin.gov or 715-634-9232

Photo of an emerald ash borer on a tree

Emerald ash borer was detected in Rusk County in northwest Wisconsin in late July, making it the 69th of Wisconsin’s 72 counties that have confirmed presence of the invasive insect. / Photo Credit: Paul Cigan, Wisconsin DNR

The emerald ash borer (EAB) has been detected for the first time in Rusk County, making it the 69th of Wisconsin’s 72 counties to determine the presence of the invasive insect.

On July 25, Wisconsin Department of Natural Resources Forest Health staff investigated a report of several ash trees with woodpecker flecking and branch dieback in a village park along Railroad Avenue in the Village of Sheldon.

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Spongy Moth Update: State Defoliation Record Set

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Photo of spongy moth laying a tan-colored egg mass on an oak tree.

A female spongy moth lays a tan-colored egg mass on an oak tree at the Kettle Moraine State Forest – Southern Unit on July 25. Photo Credit: Bill McNee, Wisconsin DNR

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

In many areas across Wisconsin, conditions were right for the worst outbreak of spongy moth caterpillars (Lymantria dispar) in more than a decade.

The caterpillars of this invasive insect — formerly known as gypsy moth — prefer to feed on oak, birch, crabapple, aspen and willow leaves, but will also feed on many other tree and shrub species. As of early August, caterpillars have pupated, but adult moths remain present.

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Balsam Fir Mortality Similar To 2018 And 2020

Posted on by akabelowsky
Picture of dying balsam fir in Northwoods of Wisconsin.

Scattered balsam fir trees in the Northwoods have suddenly turned brown and red this spring. Photo Credit: Linda Williams, Wisconsin DNR

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

Scattered balsam fir trees in some areas of northern Wisconsin have suddenly turned a rusty red or brown color and are dying. These trees are not being impacted by spruce budworm and typically die with a full complement of needles.

These symptoms are similar to those observed in 2018 and 2020. So far, the number of impacted trees reported is smaller than what was seen in 2018 or 2020. While reports of affected trees are still coming in, they seem to be concentrated in northern areas of the state that experienced extensive snowfall in late winter.

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Hemlock Being Defoliated By Spruce Budworm

Posted on by akabelowsky
Photo of spruce budworm eating hemlock needles.

Spruce budworm defoliation this spring on hemlock makes the trees look thin. Photo Credit: Linda Williams, Wisconsin DNR

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

Spruce budworm is finished feeding for the year, but the damage from the insects is still being observed.

Spruce budworm prefers to feed on balsam fir and spruce, but a previous newsletter article noted that tamarack had been observed as 100% defoliated by spruce budworm. More recently, stands of hemlock with moderate to severe defoliation were also identified.

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Basswood Thrips Causing Crumpled Leaves, Thin Crowns

Posted on by akabelowsky

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

Photo of basswood leaves damaged by basswood thrips.

Basswood leaves show damage after feeding of introduced basswood thrips. / Photo Credit: Wisconsin DNR.

For the second consecutive year, damage from introduced basswood thrips (Thrips calcaratus) is significant in some northeastern Wisconsin counties. Introduced basswood thrips are tiny, invasive insects that feed inside tree buds in early spring. Leaves are then deformed when they expand and can look like frost or wind has damaged them.

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Maple Petiole Borer Causes Leaves To Drop

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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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Lecanium Scale Creating A Sticky Situation

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

Photo showing ladybug larva feeding on lecanium scale domes.

A ladybug larva feeds on lecanium scale domes on an oak twig. / Photo Credit: Wisconsin DNR.

Lecanium scale is infesting oak forests across Marinette, Oneida and Vilas counties. These scale insects insert their mouthparts into twigs and suck the tree sap. They release honeydew, which ants can collect, or coat leaves and anything located under infested trees (i.e., yard furniture or vehicles). Sooty mold can grow on that sticky material and turn things black, so homeowners may want to rinse off the honeydew from outdoor items regularly.

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Acorn Pip Galls, Woolly Catkin Galls All The Same

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

Photo of acorns showing small pip galls.

Pip galls are small, tongue-like protrusions emerging from under the caps of acorns. / Photo Credit: Linda Williams, Wisconsin DNR.

Gall wasp life cycles can be complex. Did you know that acorn pip galls, which I’ve written about several times, have another part of their life cycle that is entirely different? This stage is called the woolly catkin gall.

Both woolly catkin galls and acorn pip galls are caused by Callirhytis quercusoperator, a species of cynipid gall wasp. This gall wasp takes two years to complete development by going through the two parts of its life cycle. Both parts of the life cycle are completed on northern red oak in our area.

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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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High Beech Scale Moving Beyond Door County

Posted on by akabelowsky

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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