Pest

Leafroller Charged With Severe Oak Defoliation

Posted on by brenna.denamur

By Paul Cigan, DNR Forest Health Specialist, Hayward, Paul.Cigan@wisconsin.gov or 715-416-4920; Mike Hillstrom, DNR Forest Health Specialist, Fitchburg, Michael.Hillstrom@wisconsin.gov or 608-513-7690; and Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665

Oak leafrollers feed on leaves and roll/fold them with strands of silk. Photo: Wisconsin DNR

An outbreak of oak leafroller moth, Archips semiferanus, has been observed in many parts of Wisconsin this year. Oak leafrollers are native, early-season defoliators. This year they have consumed and rolled up oak leaves, giving the tree crowns a thin, yellow appearance. Continue reading “Leafroller Charged With Severe Oak Defoliation” →

Lecanium Scale: A Sticky Situation

Posted on by brenna.denamur

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

Lecanium scale is popping up in a few areas of Oneida and Vilas counties. These scale insects insert their mouthparts into twigs and suck the sap of the tree. They release honeydew, which can be collected by ants or may 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 on a regular basis.

Brown lumps on a twig.

The brown lumps on this stem are lecanium scales. Photo: Wisconsin DNR

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Another Year Of Spruce Budworm Defoliation

Posted on by brenna.denamur

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

Spruce budworm is a native insect with periodic outbreaks that defoliate spruce and balsam fir in the Midwest. While these caterpillars have pupated and moths are already emerging to mate and lay eggs, spruce budworm defoliation is now becoming noticeable in northern and central Wisconsin as clipped needles stuck in caterpillar webbing turn rusty red.

Dark colored spruce budworm caterpillar feeding on new balsam fir foliage.

Spruce budworm larvae had webbed together the new growth. Note some clipped needles in the webbing that will turn rusty red in color. Photo: Wisconsin DNR

Continue reading “Another Year Of Spruce Budworm Defoliation” →

Spiny Oak Sawfly And Red Oak: A One-Sided Love Story

Posted on by brenna.denamur

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

The spiny oak sawfly feasts again. While defoliation by this insect is common in understory oaks, this year, lower branches of overstory oaks have also seen damage. All damage so far has been observed on red oaks. Previously we saw a widespread outbreak in 2005 with lesser reports of damage in 2007, 2016, 2017 and 2021.

A small caterpillar on the underside of an oak leaf.

Spiny oak sawfly larvae. Photo: Wisconsin DNR

Continue reading “Spiny Oak Sawfly And Red Oak: A One-Sided Love Story” →

Hairy Spring Caterpillars – Which One Do You Have?

Posted on by brenna.denamur

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

Wisconsin has a few leaf-eating caterpillar species that are out early in the spring. Forest tent caterpillars, eastern tent caterpillars and spongy moth caterpillars cause varying levels of tree damage and are often mistaken for one another.

A group of many forest tent caterpillars on the bark of a tree.

Forest tent caterpillars congregating on the trunk of a tree. Photo: Wisconsin DNR

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On The Lookout For Oak Wilt Fruiting Bodies

Posted on by brenna.denamur

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

Have you ever seen an oak wilt fruiting body? Oak wilt is a fungal disease that kills trees in the red oak group (northern red oak, northern pin oak, black oak and other oaks with points on their leaves). Trees in the white oak group (white oak, burr oak, swamp white oak and other oaks with rounded leaves) are more resistant to the disease, but branches or branch tips can still be killed.

A small crack in tree bark that indicates an oak wilt pressure pad is underneath.

Oak wilt pressure pads can create a crack in the bark, allowing beetles to get into the spores. Photo: Wisconsin DNR

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June To October: Oak Wilt Watch!

Posted on by brenna.denamur

By Michael Hillstrom, DNR Forest Health Specialist, Fitchburg, michael.hillstrom@wisconsin.gov

An image of two red oak leaves that are part brown and part green, symptomatic of oak wilt infection.

Typical browning leaf symptoms of red oak trees infected with oak wilt. Photo: Wisconsin DNR

Now is the time to watch for oak wilt! Symptoms typically appear in southern Wisconsin in late June and in northern Wisconsin during July. Watch for browning leaves starting at the top of the canopy and progressing downward. Most leaves will fall from infected trees as they die, typically within two to four weeks.

Several management methods are available to contain oak wilt pockets, so consult your local forest health specialist for guidance on your best options.

The forest health team is also working to evaluate new control methods. Rapid response is currently being tested to more formally evaluate if a new oak wilt infection in a single tree can be stopped before it reaches the roots and spreads to nearby oaks. There is observational data that this method works, but more formal tests are desired. Continue reading “June To October: Oak Wilt Watch!” →

Basswood Thrips: Tiny Terrors Of Basswood Leaves

Posted on by brenna.denamur

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

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.

A long and thin introduced basswood thrips rests on the underside of a small green leaf.

An adult introduced basswood thrips on the underside of an emerging basswood leaf. This photo is enlarged under a microscope. To the naked eye, they appear as tiny black specks on the underside of the leaf. Photo: Wisconsin DNR

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White Trunk Rot In Aspen Trees

Posted on by brenna.denamur

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

White trunk rot (Phellinus tremulae), sometimes called aspen trunk rot, is a fungus that causes decay columns to form in aspen. The fungus enters the tree through branch stubs, wounds or small dead branches that remain on the tree. Perennial conks, or fungal bodies, then grow from these sites.

A cross section of the trunk of an aspen with significant decay in the center and a fruiting body conk on the side of the wood.

White trunk rot causes decay in aspen trees. Note the conk (fruiting body) from the fungus on the left side of the pic. Photo: Wisconsin DNR

Continue reading “White Trunk Rot In Aspen Trees” →