Southern WI Forest Health

Oak Leaf Issues That Are Not Oak Wilt

Posted on by akabelowsky
Closeup photo showing oak wilt leaf symptoms on a red oak leaf. Leaves often show browning on the outer portions of the leaf while the base of the leaf will still have some normal green color.

Oak wilt leaf symptoms on a red oak leaf often show browning on the outer portions of the leaf while the base of the leaf will still have some normal green color. / Photo Credit: Wisconsin DNR

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

Oak wilt symptoms are active right now, but so are several other oak issues that may be mistaken for oak wilt.

Issues including Tubakia leaf spot, mite damage and leaf scorch are all causing problems in northern Wisconsin and may be mistaken for oak wilt.

Continue reading “Oak Leaf Issues That Are Not Oak Wilt” →

Periodical Cicada Damage Still Visible In Some Areas

Posted on by akabelowsky
Photo showing dieback discovered on red cedar branches in Beloit (Rock County) in August 2025.

Dieback discovered on red cedar branches in Beloit (Rock County) in August 2025. / Photo Credit: Wisconsin DNR

By River Mathieu, DNR Forest Health Specialist, Fitchburg
River.Mathieu@wisconsin.gov or 608-772-2758

In August, random branch dieback was observed by a Wisconsin Department of Natural Resources forester on red cedars in a 10-acre stand near Beloit in Rock County.

At first, the pattern of dieback was perplexing. Based on a photograph, the damage was first presumed to be caused by a fungal disease. Once a site visit was conducted, it was determined that the branch dieback was caused by cicada oviposition (egg-laying) damage from last year’s emergence of periodical cicadas.

Continue reading “Periodical Cicada Damage Still Visible In Some Areas” →

Jack Pine Showing Dead, Brown Branch Tips

Posted on by akabelowsky
Photo showing jack pine branch tips killed by the jack pine tip beetle.

Jack pine branch tips killed by the jack pine tip beetle. / Photo Credit: Wisconsin DNR

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

Jack pine tip beetle (Conopthorus banksianae) is a tiny bark beetle that bores into the twig tips of pines. Damage from jack pine tip beetle was observed this summer on jack pine in Vilas County. In some areas, each tree showed 2-10 dead branch tips in its crown.

Continue reading “Jack Pine Showing Dead, Brown Branch Tips” →

Barklice Don’t Damage Trees

Posted on by akabelowsky
Photo showing a group of immature bark lice show their characteristic striped abdomens.

A group of immature barklice show their characteristic striped abdomens. / Photo Credit: Wisconsin DNR

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

Barklice, sometimes called tree cattle, tend to congregate in large groups on trees, which can lead some people to worry about tree health. However, they are actually quite harmless.

Immature barklice don’t have wings, so you can see their heavily striped abdomens. Adults have dark-colored wings that form a tent over the abdomen. Both immature and adult barklice congregate in groups.

These insects feed on the algae, lichen and other debris that collects on the surface of tree bark. They do not feed on the tree itself.

Continue reading “Barklice Don’t Damage Trees” →

Sawflies On Jack Pine Are Neodiprion Maurus

Posted on by akabelowsky
Photo showing five Neodiprion maurus larvae feeding on jack pine needles.

Neodiprion maurus larvae, feeding on jack pine, are gregarious. Can you spot all five larvae? / Photo Credit: Wisconsin DNR

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

In mid-July, a few sawfly larvae were found feeding on jack pine in northern Vilas County. After delving into associated literature and reaching out to a sawfly researcher at the University of Kentucky, the sawflies were identified as Neodiprion maurus. There is no official common name for this insect; it is generally referred to as “a sawfly on jack pine.”

These sawflies are gregarious and feed in groups on older needles, doing relatively minimal damage. They are often referred to as “rare” and have been found in Michigan, Minnesota and Wisconsin, as well as Alberta, Manitoba and Saskatchewan in Canada.

Continue reading “Sawflies On Jack Pine Are Neodiprion Maurus” →

Pink Striped Oakworm Seen Feeding On Red Oaks

Posted on by akabelowsky
Closeup photo showing young pink striped oakworm caterpillars feed gregariously on northern red oak leaves.

Young pink striped oakworm caterpillars feed gregariously on northern red oak leaves. / Photo Credit: Wisconsin DNR

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

Young larvae of the pink striped oakworm (Anisota virginiensis) have been observed feeding gregariously on northern red oak leaves in Vilas County. Northern red oak is their preferred host, but they can feed on other oaks.

Young caterpillars start life with a shiny black head capsule, but older larvae develop an orange head. Their pinkish body coloration develops as they get older, as well; young caterpillars are dark green in color.

Pink striped oakworm has several fly parasitoids, along with a couple of wasp parasitoids. Populations of pink striped oakworm in Wisconsin don’t usually grow too large or cause problems.

 

Northern Pitch Twig Moth Creates Pitch Blisters On Jack Pine

Posted on by akabelowsky
Closeup photo showing that hollow pitch blisters get darker with age and may resemble cones until closer examination.

Hollow pitch blisters get darker with age and may resemble cones until closer examination. / Photo Credit: Wisconsin DNR

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

Northern pitch twig moth (Petrova alhicapitana) is also called the pitch nodule maker or pitch blister moth.

It feeds on branches and twigs of young jack pine and scotch pine, causing a hollow blister of gooey pitch to form around the larvae as it feeds at the base of a lateral branch. It prefers trees that are 20 feet tall or smaller, although it can attack older trees.

Continue reading “Northern Pitch Twig Moth Creates Pitch Blisters On Jack Pine” →

Native Sawyer Beetles Resemble Asian Longhorned Beetle

Posted on by akabelowsky
An adult Asian longhorned beetle, left, and an adult whitespotted sawyer beetle, right. The arrow shows the white spot at the top of the whitespotted sawyer beetle’s wing covers, indicating it’s the native beetle and not Asian longhorned beetle. / Photo Credits: Left, Bugwood.org; right, Wisconsin DNR

Two closeup photos show the similarities and differences between an adult Asian longhorned beetle, left, with spots all over its back and striped antennae; and an adult whitespotted sawyer beetle, right, with one white spot beneath its head and between its wings.

By Michael Hillstrom, DNR Invasive Forest Pest Coordinator
Michael.Hillstrom@wisconsin.gov

More than 300 species of longhorn beetles inhabit the Midwest. The Wisconsin Department of Natural Resources (DNR) posted about one species, the invasive Asian longhorned beetle (ALB), on social media in early July.

Forest Health staff received many photos of potential ALB as a result. Fortunately, none of the photos were of ALB – which has yet to be detected in Wisconsin.

By far, the most common insect seen in the submitted photographs was a native longhorn species called the whitespotted sawyer beetle (Monochamus scutellatus), also known as a pine sawyer beetle.

Continue reading “Native Sawyer Beetles Resemble Asian Longhorned Beetle” →

Herbicide Damage To Trees? Always Read The Label

Posted on by akabelowsky
Closeup photo showing active ingredients listed on the front label of pesticide containers. The complete label, including instructions, may be on the front or back of the bottle and will require opening to read.

Active ingredients are listed on the front of pesticide containers (yellow arrow above). The complete label, including instructions, may be on the front or back of the bottle and will require opening to read (blue arrow above). / Photo Credit: Wisconsin DNR

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

This is your reminder to always read pesticide labels, even if you think the product you are using is the same product you’ve always used.

Do you always check the active ingredients listed on the front of pesticide containers – and read instructions on the use of the product – every time you buy a new container of pesticide? It has become more important than ever to do so.

Continue reading “Herbicide Damage To Trees? Always Read The Label” →

Japanese Beetle Defoliates Some Forest Trees In The North

Posted on by akabelowsky
Closeup photo of Japanese beetles defoliating a basswood leaf

Japanese beetles defoliating a basswood leaf. / Photo Credit: Wisconsin DNR

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

The Japanese beetle (Popillia japonica) is an invasive insect that feeds on many plant species. The adult beetles “skeletonize” leaves by eating the material between the veins.

Adult Japanese beetles feed on the flowers and leaves of more than 300 plant species, including trees, shrubs and herbaceous plants. Forest trees can be defoliated, with open-grown or edge trees suffering the highest defoliation rates.

Japanese beetles favor birch, mountain ash and basswood (linden) trees, but they have also been observed feeding on the leaves of young oaks.

Continue reading “Japanese Beetle Defoliates Some Forest Trees In The North” →