Pest

Squirrel Damage Mayhem

By Linda Williams, DNR Forest Health Specialist, Woodruff

Linda.Williams@wisconsin.gov or 920-360-0665

Finger pointing at tooth marks on the wood of a maple that squirrels stripped of bark.

Narrow grooves are left when squirrels chew the bark off a young tree or a branch.
Photo: Wisconsin DNR

In late winter, it’s common to see tree branches that have been freshly stripped of their bark. Damage can be extensive where entire branches, and sometimes entire small trees, can be stripped of bark. This damage, believe it or not, is from squirrels! While primarily found on sugar maples, you can also find squirrel damage on red maples and the occasional oak. So far this year, the damage has been noted in Langlade, Shawano, Oneida and Vilas Counties. 

On sunny days, the pale wood of branches where the bark has been stripped off stands out in the forest. This type of feeding can remove enough bark to girdle the branches or the main stem, causing the tree to die from that point to the end of the branch. Branches that are not entirely girdled will continue to grow, and callus tissue will begin to grow over the wounds. If branches are nearly girdled, they may leaf out in the spring only to have the leaves suddenly wilt and die as hot weather hits because the tree can’t move enough water to keep the leaves alive. Continue reading “Squirrel Damage Mayhem”

Protect Your Valuable Ash Trees Against Emerald Ash Borer

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

Property owners with healthy, valuable ash trees are encouraged to treat them with insecticide this spring to protect against emerald ash borer (EAB). The pest is currently the most damaging threat to trees in Wisconsin, killing more than 99% of the ash trees it infests.

Ash tree branch in West Allis has been damaged by woodpeckers. Sections of bark are missing or have been flecked away.

This ash tree branch in West Allis has been damaged (“flecked”) by woodpeckers feeding on EAB larvae under the bark.
Photo: Bill McNee, Wisconsin DNR

Continue reading “Protect Your Valuable Ash Trees Against Emerald Ash Borer”

One Last Chance To Treat Or Remove Spongy Moth Egg Masses; DATCP Slow-The-Spread Aerial Treatments Announced

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

Three tan-colored lumps about the size of a nickel or a quarter are spongy moth egg masses on the underside of a pine branch in Walworth County.

Three spongy moth egg masses on the underside of a pine branch in Walworth County.
Photo: Bill McNee, Wisconsin DNR

Spongy moth* (formerly known as gypsy moth) egg masses typically begin to hatch in April as temperatures warm. Now is a great time to inspect your trees for egg masses and treat or remove any masses within reach. Each mass that hatches may produce up to 1,000 leaf-eating caterpillars.

Populations of spongy moths increased in 2020 and 2021 due to favorable weather conditions. This winter’s temperatures have not been cold enough to cause heavy egg mortality. A large rise in caterpillar numbers can be expected in 2022 if weather conditions are warm and dry over the next few months.

Continue reading “One Last Chance To Treat Or Remove Spongy Moth Egg Masses; DATCP Slow-The-Spread Aerial Treatments Announced”

EAB Identified In Lincoln County For The First Time, Continues Spread Into Northern Wisconsin

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

Emerald ash borer (EAB) continues to spread into areas of Northern Wisconsin and was detected for the first time in Lincoln County, in the Town of Harrison and the City of Tomahawk. EAB was first identified in Wisconsin in 2008, only 14 years ago. It is now in 62 of Wisconsin’s 72 counties.

S-shaped markings in an ash tree trunk where a hatchet has removed the bark.

S-shaped galleries under the bark of this ash were created by EAB larvae. You can also see epicormic branches (water sprouts) coming out of the trunk. These are a sign of significant stress in the tree. Photo Credit: Wisconsin DNR

Continue reading “EAB Identified In Lincoln County For The First Time, Continues Spread Into Northern Wisconsin”

Prune Oak Trees In Winter To Help Prevent Oak Wilt

By Kyoko Scanlon, DNR Forest Pathologist, Fitchburg, Kyoko.Scanlon@wisconsin.gov; and Paul Cigan, DNR Forest Health Specialist, Hayward, Paul.Cigan@wisconsin.gov

Person uses branch cutters to prune oak tree with brown leaves during the winter.

Prune oak trees during winter when oak wilt disease-carrying insects are inactive. Photo credit: Wisconsin DNR

Start the year off by pruning your trees to protect them from harmful pests that emerge after the thaw. Continue reading “Prune Oak Trees In Winter To Help Prevent Oak Wilt”

Acorn Weevils Make Acorns Float

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

Have you seen small round holes in acorns? These holes are a sign of acorn weevil damage that can occur in all Wisconsin oak species.

In a pile of brown and tan acorns, two have small round pencil-tip sized holes caused by acorn weevil larvae burrowing out from the inside.

Two acorns show exit holes of acorn weevils. / Photo Credit: Wisconsin DNR

Continue reading “Acorn Weevils Make Acorns Float”

Take Action! Look For Gypsy Moth Egg Masses

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

In 2021, gypsy moth populations increased for a second consecutive summer due to favorable weather conditions. Populations typically increase with an average or mild winter, below average spring precipitation and above average May through June temperatures.

Regional variation in weather can result in significant differences in populations. If weather conditions are favorable again in 2022, the most noticeable increase in caterpillar numbers would likely occur in southern counties, where conditions were driest during this past spring and summer.

Populations experience the fastest growth rate and are first noticed on:

  • Dry sites with sandy soil and abundant oak
  • Mowed lawns with preferred tree species (oak, crabapple, birch, etc.)
  • Large oaks (bur, in particular) with rough bark, especially on or adjacent to mowed lawns
Five small gypsy moth egg tan masses on a single tree branch in Walworth County.

Gypsy moth egg masses found in Walworth County in fall 2021.
Photo Credit: Gypsy moth egg masses KMSU

 

 

 

 

 

 

 

 

 

 

 

 

Continue reading “Take Action! Look For Gypsy Moth Egg Masses”

Managing Damage By White Pine Weevil

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

Tree damage from white pine weevil is noticeable across Wisconsin this time of year. White pine weevils attack several different Wisconsin species, including eastern white pine, jack pine and spruce.

Adult weevils lay their eggs on terminal leaders in the spring. After the eggs hatch, larvae bore into the terminal and begin feeding downwards just under the bark which can result in the killing of a 1 to 2-feet section of the terminal leader as they feed. Terminal leaders will often have a wilted or “shepherds crook” appearance, and they will turn rusty red to brown late in the fall season. These dead terminal leaders will often break off during the winter.

A white pine tree with a cluster of dead twigs caused by a white pine weevil attack.

Dead terminal leader caused by a white pine weevil attack on a young white pine.
Photo Credit: Wisconsin DNR

Continue reading “Managing Damage By White Pine Weevil”

Mystery Walnut Defoliator Identified

Article by: Mike Hillstrom, Forest Health Specialist

In 2020, forest health staff in Wisconsin, Minnesota and Iowa received calls about black walnut stands being defoliated and webbed. In 2021, the defoliation expanded to multiple additional black walnut stands in southwest Wisconsin, while northeast Iowa and Minnesota continued to see damage. Recently, molecular work completed by the Wisconsin Department of Agriculture, Trade and Consumer Protection has identified the larvae causing the damage as a native Tortricid moth, Gretchena amatana.

G. amatana caterpillars on tree.

G. amatana caterpillars on tree.

Fine webbing covers walnut tree trunk.

Fine webbing covers walnut tree trunk.

 

 

 

 

 

 

 

 

 

 

 

Continue reading “Mystery Walnut Defoliator Identified”

Young Oaks Defoliated By Oak Slug Sawfly

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

The oak slug sawfly (Caliroa quercuscoccineae), sometimes called the scarlet oak sawfly, has the appearance of a small, slimy slug. Its slime helps it stick to leaves it feeds on. The oak slug sawfly’s tiny larvae feed in groups on the undersides of oak leaves, scraping out the green material from between the veins of the leaves. The upper leaf surface is usually left intact, creating a “stained glass window” look. Oak slug sawfly has the ability to completely defoliate leaves before dropping to the ground to pupate.

Two oak leaves eaten by oak slug sawfly larvae left with brown discoloration on the leaf and translucent patches.

Oak slug sawfly larvae cause defoliation on oak leaf after feeding.
Photo Credit: Wisconsin DNR

Continue reading “Young Oaks Defoliated By Oak Slug Sawfly”