Did you know?

Catastrophic Hail Injury To Trees In Northwest Wisconsin

Posted on by brenna.denamur

By Paul Cigan, DNR Forest Health Specialist, Hayward, Paul.Cigan@wisconsin.gov or 715-416-4920

Conifer and hardwood trees have begun showing more apparent and often substantial signs and symptoms of damage from a severe hailstorm that spread across several northwestern Wisconsin counties on May 9, 2022.

The storm produced golf ball-size hailstones and high-speed winds causing catastrophic injury to tree branches and stems, in addition to defoliation. Few tree species were spared in its path. The heaviest impact occurred in northeastern Polk County, where defoliation of aspen and black locust reached nearly 100%, and pine exceeded 90% (Fig. 1). Red and white oaks show more moderate damage.

Aspen trees nearly entirely defoliated.

Figure 1. Polk County had nearly 100% defoliation from a severe May hailstorm. Photo: Wisconsin DNR

Continue reading “Catastrophic Hail Injury To Trees In Northwest Wisconsin” →

Giant Hogweed Or Cow Parsnip?

Posted on by brenna.denamur

By Jaqi Christopher, DNR Forest Invasive Plant Specialist, Rhinelander, Jacquelyn.christopher@wisconsin.gov

Giant hogweed is a large invasive species commonly confused with the native look-alike cow parsnip. Although giant hogweed is uncommon in Wisconsin, it’s important to know the difference between the two.

Person standing with giant hogweed towering over them.

Giant hogweed can invade woodlots and get 8-20 feet tall. Photo Credit: Ramona Shackleford

Continue reading “Giant Hogweed Or Cow Parsnip?” →

20 Year Anniversary Of Emerald Ash Borer Confirmation In North America

Posted on by brenna.denamur

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

Five metallic green beetles against a white background.

Early photo of EAB adults taken in June 2002, prior to the insect species being identified. Photo: USDA Animal and Plant Health Inspection Service

The beginning of July marked 20 years since we received news of an unidentified beetle that turned out to be the emerald ash borer (EAB), one of North America’s greatest tree killers. On July 1, 2002, DNR forest health staff received an email from USDA Animal and Plant Health Inspection Service about this beetle being associated with declining ash in southeast Michigan:

This is to notify you that in the past few days we have responded to a report of an insect pest feeding on ash in the western suburbs of Detroit. This follows what has been a series of reports of declining ash in this area over the past couple of years. However, in the past we have not been able to associate it with any particular insect or disease. We are now seeing a boring insect emerging from the infested trees in various sites… The adult, which is emerging now, resembles the shape and size of two lined chestnut borer. It is emerald, metallic green in color and leaves a D-shaped exit hole, similar to bronze birch borer… Continue reading “20 Year Anniversary Of Emerald Ash Borer Confirmation In North America” →

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” →

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

Continue reading “On The Lookout For Oak Wilt Fruiting Bodies” →

I Spy… Browning White Pine Stands Along Roads

Posted on by brenna.denamur

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

As you begin your summer travel, you may notice that many white pine trees along northern Wisconsin roadways have a lot of brown needles on them. Although it may seem concerning, most of these trees are sending out new needles as we speak.

Three young conifers with varying levels of browning needles

Different conifer species can be impacted differently by salt spray. The white pine in the middle also shows lower branches that are green because they were protected by snow. Photo: Wisconsin DNR.

Continue reading “I Spy… Browning White Pine Stands Along Roads” →

Slow Oaks And Maples With Too Many Seeds And Not Enough Leaves

Posted on by brenna.denamur

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

Maples

Have you noticed any maple trees that appear brown or reddish and have fewer leaves than usual? The seeds, not the leaves, make the tan/red color. Those seeds are so plentiful this year that they can easily be spotted from a distance.

Reddish tan maple trees with thin canopies.

Maples with heavy seed crops may appear tan or reddish due to the color of the seeds and having very few green leaves in the canopy. Photo: Wisconsin DNR.

Continue reading “Slow Oaks And Maples With Too Many Seeds And Not Enough Leaves” →

Spring Cleaning: Storm Damage Cleanup Brings Oak Wilt Risk

Posted on by brenna.denamur

By Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665 & Paul Cigan, DNR Forest Health Specialist, Hayward, Paul.Cigan@wisconsin.gov, 715-416-4920.

Spring cleanup is always a busy time in the Northwoods as those with second homes and cabins make the trek northward to prepare for a summer of fun. For many, this will mean cleaning up trees and branches damaged by winter storms.

A forested scene with broken branches at the base of a white pine tree.

Large white pines (pictured here) and young birch growing on forest edges were most heavily impacted by winter’s storms. Photo: Wisconsin DNR

Continue reading “Spring Cleaning: Storm Damage Cleanup Brings Oak Wilt Risk” →

April Showers Bring May Garlic Mustard

Posted on by brenna.denamur

By Brenna DeNamur, DNR Forest Health Outreach Specialist, Madison, Brenna.DeNamur@wisconsin.gov; Jaqi Christopher, DNR Forest Invasive Plant Specialist, Rhinelander, Jacquelyn.Christopher@wisconsin.gov; & Mary Bartkowiak, DNR Forest Invasive Plant Coordinator, Rhinelander, Mary.Bartkowiak@wisconsin.gov

Spring is here! Invasive plants, like garlic mustard, are often among the first green life to emerge in the new season.

A dense population of garlic mustard carpets a forest floor.

Garlic mustard is an invasive plant that appears early in spring. Photo: Wisconsin DNR

Continue reading “April Showers Bring May Garlic Mustard” →

Help Protect Oak Trees From Oak Wilt

Posted on by brenna.denamur

Contact: Paul Cigan, DNR Forest Health Specialist

Paul.Cigan@wisconsin.gov or 715-416-4920

As April brings a high risk of the often-fatal oak wilt disease, the Wisconsin Department of Natural Resources (DNR) recommends not pruning or cutting oaks from April through July.

A large oak tree in a wooded area has fresh wounds from branches being sawed off.

Do not prune, cut or wound oaks April through July.
Photo: Linda Williams

Continue reading “Help Protect Oak Trees From Oak Wilt” →