Oak Wilt Confirmed In Ashland County

Map showing Wisconsin counties in which oak wilt has been detected.

With the addition of Ashland County, oak wilt has now been detected in 66 of Wisconsin’s 72 counties. / Map Credit: Wisconsin DNR.

By Paul Cigan, DNR Forest Health Specialist, Hayward or 715-416-4920

Oak wilt, a deadly disease of oaks, has been found for the first time in Ashland County.

The Wisconsin Department of Natural Resources (DNR) confirmed the find in wood samples from a red oak tree in the town of Gordon.

“There is always risk of oak wilt spread into new and relatively uninfested areas in northern Wisconsin, such as Ashland County, so it’s always best to practice oak wilt prevention wherever possible to significantly reduce that risk,” said Paul Cigan, a DNR forest health specialist based in Hayward.

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Don’t Let Tree Trouble Hitch A Ride On Firewood

Photo of spongy moth egg masses attached to a piece of firewood

A pair of spongy moth egg masses attached to a piece of firewood. Moving this firewood to another site could put trees at that site at risk in the spring. / Photo Credit: Wisconsin DNR

By Art Kabelowsky, DNR Forest Health Outreach/Communications or 608-335-0167

Are you generally hesitant to give hitchhikers a free ride?

October was National Firewood Awareness Month, and even though November has arrived, the Wisconsin Department of Natural Resources (DNR) continues to urge residents and visitors to follow the same line of thinking when it comes to moving firewood.

That’s because tree-killing hitchhikers often lurk on or in firewood — including spongy moth, emerald ash borer, the fungus that causes oak wilt and other invasive insects and fungi. When untreated, infested firewood is transported away from where the tree died, those pests and fungi can later emerge to attack trees at the new site. This can happen whether that new location is in the next town or hundreds of miles away.

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Protect Oaks During Spring Clean-up

By Paul Cigan, DNR plant pest and disease specialist, or 715-416-4920

An oak tree with branches trimmed

To prevent the spread of often-fatal oak wilt disease, do not prune, cut or wound oaks from April through July. Photo: Wisconsin DNR

With the arrival of spring, the Wisconsin Department of Natural Resources (DNR) recommends protecting oaks from the often-fatal oak wilt disease by refraining from pruning, cutting or injuring oak trees from April through July.

The highest risk period for oak wilt introduction to a new site is in spring and early summer. Pruning and cutting oaks exposes living tree tissue beneath the bark to potential infection. The disease rapidly kills trees in the red oak group and weakens those in the white oak group.

Sap-feeding beetles spread the disease between oaks by carrying oak wilt spores from infected trees or firewood to fresh, exposed tree wounds. Healthy oaks and freshly cut oak stumps can become infected as quickly as 15 minutes after a wound is made from a pruning cut or broken branch.

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Moving Firewood Can Spread Invasive Species

An image of an insect walking away from burning firewood in a forest with the caption, “Buy it where you burn it.”

Don’t Move Firewood, The Nature Conservancy

October is Firewood Month! Help prevent the spread of invasive insects and diseases by buying firewood where you burn it.

Firewood Scout can help you find local firewood for sale.

See the DNR website for more information on invasive species and forest health. Continue reading “Moving Firewood Can Spread Invasive Species”

Avoid Ash Trees When Placing Deer Stands

By Bill McNee, DNR Forest Health Specialist, or 920-360-0942

The Wisconsin Department of Natural Resources (DNR) cautions hunters to avoid placing deer stands in or near ash trees this deer season as they start scouting properties.

Hunter in trees

It is important to place and maintain tree stands carefully as you prepare for this upcoming hunting season. Photo Credit: Wisconsin DNR

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Spring Cleaning: Storm Damage Cleanup Brings Oak Wilt Risk

By Linda Williams, DNR Forest Health Specialist, Woodruff,, 920-360-0665 & Paul Cigan, DNR Forest Health Specialist, Hayward,, 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

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EAB Found In Barron County

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

Emerald ash borer (EAB) has been discovered for the first time in Barron County, in the town of Lakeland. Dead and dying green ash were observed and larval specimens were subsequently lab-confirmed. Most of the green ash across a 20-acre area are either dead or dying from EAB attack.

Dead and dying green ash trees with characteristic woodpecker damage

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Oak Wilt Symptoms Visible Now

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

Symptoms of oak wilt are showing up. Look for leaves that suddenly wilt and drop from the tree. Oak wilt is a non-curable, fungal disease specific to oaks. Trees in the red oak family will die quickly from this disease, while trees in the white oak family will die more slowly, with a branch or portion of the crown becoming infected. 

This tree is actively wilting from oak wilt infection and will drop most of its leaves within about 4-6 weeks.

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Oak Timberworm, Not Your Average Weevil

By Linda Williams, DNR Forest Health Specialist, Woodruff, or 920-360-0665

Oak timberworm, Arrhenodes minutus, is a primitive weevil that can cause defects and degrade in red and white oak timber. They can also infest elm, poplar and beech. Egg-laying females will seek out trees that are damaged, wounded, nearly dead or recently dead. After the eggs hatch, the larvae bore across the grain through the tree then “U-turn” back across the grain to the point of origin, taking two or three years to complete their life cycle and creating a lumber defect called a wormhole. When infested wood is split for firewood, the weevils may emerge in homes or garages if they had already pupated when the firewood was split. 

Male oak timberworm on a Northern red oak that was damaged in a storm.

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Emerald Ash Borer Identified In Iron County For The First Time

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

Emerald ash borer (EAB) has been detected for the first time in Iron County, in the Town of Oma. Many of the black ash at this site are already dead, with other trees still declining. EAB was first identified in Wisconsin in 2008 and has now been found in 60 of Wisconsin’s 72 counties.

Did you know that it takes fewer EAB larvae to attack and kill a black ash compared to a green ash or white ash? This means that black ash will have fewer galleries under the bark and consequently less woodpecker flecking than you would typically see with green ash or white ash. 

EAB was federally deregulated as of Jan. 14, 2021 and Wisconsin instituted a state-wide quarantine in 2018, so there are no regulatory changes due to this find. Emerald ash borer silviculture guidelines were created to help landowners make decisions about management in their woods. All forest sites are a bit different and it can be overwhelming to try to decide what management, if any, should be done in your stand and these guidelines are designed to help answer those questions.

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