Pest

Spruce budworm defoliation showing up

Posted on by margueriterapp

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

Spruce budworm defoliation is becoming noticeable in northern and central Wisconsin counties as clipped host tree foliage stuck in the caterpillars’ webbing turns rusty red. The caterpillars should pupate soon, and moths will emerge a couple weeks later to mate and lay eggs. Spruce budworm is a native insect with periodic outbreaks that defoliates spruce and balsam fir in the Midwest.

Close-up of spruce budworm caterpillar near the silk web it spins around branch tips.

Spruce budworm caterpillar near the silk webbing it spins on branch tips.

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Pine tortoise scale can cause branch and tree mortality, sooty mold problems

Posted on by margueriterapp

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

Pine tortoise scales are sometimes found at very heavy densities on jack and scotch pine twigs. In Wisconsin they prefer young jack pine trees, inserting their straw-like mouthparts into twigs and sucking out the sap. When populations are high, pine tortoise scale can cause branch mortality and even whole tree decline.

Tiny pine tortoise scales clustered on a pine branch tip.

Pine tortoise scales are so plentiful on this twig that they are practically on top of one another.

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USDA seeks ash trees to battle EAB

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Emerald ash borer (EAB) is an invasive insect from Asia that was first introduced into the United States in 2002. Since its discovery, EAB has caused the death and decline of tens of millions of ash trees. Today, the U.S. Department of Agriculture (USDA) is using ash trees against the pest to help preserve and protect the tree species. Staff in the USDA EAB biological control (biocontrol) program are asking Wisconsin landowners in Sheboygan, Fond du Lac and Door counties to help by donating infested ash trees for use in raising wasps that attack and kill EAB.

A square window of bark is removed from green ash to uncover EAB larvae underneath.

USDA staff cut a “bark window” in green ash to uncover signs of EAB.

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Proposed guidance available for public comment

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By Bill McNee, forest health specialist, Oshkosh, Bill.Mcnee@wisconsin.gov, 920-360-0942

The DNR Forest Health Program currently has proposed guidance, “Organizing an aerial spray for forest pests: Recommendations and regulations,” available for public comment until May 25. The document can be found on the proposed DNR program guidance webpage under “new proposed program guidance.” Comments can be submitted through this webpage.

Cover page of proposed aerial spray guide.

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Two-lined chestnut borer in flooded oak stands

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By Mike Hillstrom, forest health specialist, Fitchburg, Michael.Hillstrom@wisconsin.gov, 608-513-7690

2019 was the wettest year ever recorded in Wisconsin. Four of Wisconsin’s top five wettest years have taken place in the last decade, three of them in the last five years: 2019, 2018 and 2016. Flooding can be stressful for trees, and with flooding occurring over the past few years in many parts of the state, forest health staff expect the impacts to forests to continue to escalate. Continue reading “Two-lined chestnut borer in flooded oak stands” →

White pine blister rust can girdle branches

Posted on by margueriterapp

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

White pine branches that suddenly turn red may be a sign of white pine blister rust. White pine blister rust is a fungal infection that creates expanding “dead spots” or cankers on the branches or main stem of host trees. Eventually the fungus grows enough to girdle the branch or main stem and the needles fade from green to pale green to rusty red. Orange, spore-producing pustules erupt around the edges of the canker in the spring.

Orange pustules erupt through the bark and around the margins of a white pine blister rust canker. Photo by Jean Romback-Bartels.

Orange pustules erupt through the bark and around the margins of a white pine blister rust canker. Photo by Jean Romback-Bartels.

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Gypsy moth spray program begins in May

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The 2020 gypsy moth slow-the-spread program, operated by the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) is expected to begin aerial spraying in the second half of May to slow the westward spread of gypsy moth.

Map of counties to be sprayed in 2020.

Map of counties where slow-the-spread treatments will occur in 2020.

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Gall rusts on jack pine

Posted on by margueriterapp

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

There are three things you may find interesting about gall rusts on jack pine at this time of year. The first is that as winter recedes, closer examination of the galls on jack pine shows that squirrels like to chew on them. The squirrels seem to prefer the smaller galls, with most chewing marks being observed on galls less than 2” in diameter. They eat the galls by scraping off the outer layers, leaving behind telltale teeth marks.

Chewing marks on a branch gall caused by gall rust.

Squirrels sometimes feed on galls, scraping away the outer layers and leaving teeth marks behind.

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Mouse, rabbit and squirrel damage from winter

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By Todd Lanigan, forest health specialist, Eau Claire, Todd.Lanigan@wisconsin.gov, 715-210-0150

With the onset of spring and snow melt, you may have noticed bark missing at the base of trees and shrubs. This is most commonly noticed on sections of bark that were below the snow line. This damage, known as girdling, was caused by mice and rabbits feeding on the bark during the winter.

Girdling damage at base of tree surrounded by older greyish black wound.

Mouse girdling damage at base of tree surrounded by older greyish-black wound.

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Prepare for the return of gypsy moths in spring

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By Bill McNee, DNR forest health specialist, Oshkosh, bill.mcnee@wisconsin.gov, 920-360-0942

Gypsy moth eggs are expected to start hatching as temperatures warm in the next few weeks. Now is a great time for homeowners to check their trees for egg masses and treat or remove any that are found. Removing the egg masses now will help protect trees from defoliation and reduce future caterpillar populations.

Gypsy moth larvae hatching from egg masses on an outdoor bowl.

Gypsy moth larvae hatching from egg masses on an outdoor bowl.

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