Woodland owners

Fungicide For HRD Stump Treatment Available In Smaller Size

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A bag of Tim-bor Professional, a borate-based chemical that fights Heterobasidion root disease. / Photo Credit: Wisconsin DNR

By Kyoko Scanlon, Forest Pathologist, Fitchburg
Kyoko.Scanlon@wisconsin.gov

People who have been dealing with Heterobasidion Root Disease (HRD) may be familiar with the product name “Cellu-Treat®.” It has been used to treat fresh cut stumps to prevent HRD.

But Cellu-Treat® is not the only chemical available for HRD. Another borate-based chemical, Tim-bor® Professional, can also be used legally for the same purpose in Wisconsin. Both products are manufactured by Nisus Corporation, and their labels are almost identical (Cellu-Treat label, Tim-bor label).

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Species Spotlight: Japanese Honeysuckle

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Japanese honeysuckle climbing up nearby trees. / Photo Credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

By Carter Hellenbrand, DNR Invasive Plant Field Specialist, Fitchburg
Carter.Hellenbrand@Wisconsin.gov  

Note: This is the first installment in the Forest Health News “Invasives Spotlight” series, a monthly series of Forest Health News articles.

Many people recognize honeysuckle as a fast-spreading invasive shrub that can quickly displace native vegetation. But did you know that some honeysuckles exist as a vine?

Japanese honeysuckle (Lonicera japonica) is an invasive perennial vine that can grow to a length of 80 feet or longer. Birds will often eat and disperse the berries the vine produces, allowing for the creation of new populations.

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‘Exploding Trees’ Face Long-term Impacts

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A long vertical wound in a tree trunk caused by deep freezing.

Cracked bark and wood creates a long vertical wound typical of the phenomenon commonly called “exploding trees.” / Photo Credit: Wisconsin DNR

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

This past winter, “exploding trees” went viral on social media. Many news outlets followed up with a more realistic explanation of the dramatically named phenomenon, pointing out that while the bitter cold can cause sudden cracks to form on trees, the trees don’t truly explode.

But what happens to those damaged trees as we warm up and move into the growing season?

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Look For Spongy Moth Egg Masses And Take Action

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Closeup of a person scraping spongy moth egg masses into a cup.

A putty knife, plastic knife or similar object can be used to gently scrape spongy moth egg masses into a cup of soapy water. The water can be discarded after two days. / Photo Credit: Wisconsin DNR

By Bill McNee, DNR Forest Health Specialist, Oshkosh
Bill.McNee@wisconsin.gov

The Wisconsin Department of Natural Resources (DNR) encourages property owners to examine their trees for spongy moth egg masses and determine whether control measures are needed this spring.

Property owners who have oak, birch, crabapple, aspen, willow and linden (basswood) trees should be particularly watchful because the caterpillars of this invasive insect prefer these species. However, they will feed on many other kinds of trees and shrubs.

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Oak Wilt Information Updated

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University of Wisconsin-Madison Extension online tool to help with oak wilt decisions.

A University of Wisconsin-Madison Extension online tool provides users localized information about the estimated emergence status of the two most important insects that transmit oak wilt in Wisconsin. / Graphic Credit: University of Wisconsin-Madison Extension

By Kyoko Scanlon, DNR Forest Pathologist, Fitchburg
Kyoko.Scanlon@wisconsin.gov

In 2025, oak wilt was detected for the first time in Hughes Township, Bayfield County, a northern Wisconsin location where oak wilt remains uncommon. There were no new county finds in 2025.

Based on the findings in 2025, the maps in the Oak Harvesting Guidelines To Reduce The Risk Of Introduction And Spread Of Oak Wilt (the oak wilt guidelines), oak wilt fact sheet and were updated. The maps in the oak wilt guidelines are good through the end of 2026.

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Oak Wilt High Risk Period Quickly Approaches

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A closeup of a fungal pressure pad under the bark of an oak tree infected with oak wilt.

A fungal pressure pad formed on the outside of the sapwood underneath the bark of an infected tree. The pad will create cracks in the bark, where beetles can enter and visit the pad and become covered in spores. They will then leave and move on to infect new trees through open wounds. / Photo Credit: Wisconsin DNR

By Alex Hornung, DNR Forest Health Specialist, Plover
Alexandra.Hornung@wisconsin.gov or 715-340-3810

It is again that time of year to pause operating in oak stands or pruning oak trees during the high-risk period for oak wilt, which begins in April. The high-risk period begins April 1 in the South, April 15 in the North, and ends in both zones on July 15.

The high-risk period is determined by when the beetles that carry the fungus that causes oak wilt have emerged for the year and when they are carrying the highest number of fungal spores. When wounds are created by logging operations or other activities that expose sapwood, the beetles carry the fungus to the wounded tree, and the disease process begins.

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Forest Health Annual Report Hot Off The Presses

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The cover of the 2025 Wisconsin Department of Natural Resources Forest Health Annual Report.

The cover of the 2025 Wisconsin Department of Natural Resources Forest Health Annual Report. / Graphic Credit: Wisconsin DNR

By Art Kabelowsky, DNR Outreach and Communications, Fitchburg
Arthur.Kabelowsky@wisconsin.gov or 608-335-0167

The Wisconsin Department of Natural Resources (DNR) has made its 2025 Forest Health Annual Report ready to view and download.

This year’s edition contains 55 pages of reporting on forest health issues throughout Wisconsin, detailing methods employed by the DNR and other agencies to control pests, diseases and invasive plants.

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Shively, McNee To Make Public Appearances

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Tim Shively, the Wisconsin Department of Natural Resources Forest Health specialist for the West Central zone.

Tim Shively, the Wisconsin Department of Natural Resources Forest Health specialist for the West Central zone. / Photo Credit: Wisconsin DNR

By Art Kabelowsky, DNR Outreach and Communications, Fitchburg
Arthur.Kabelowsky@wisconsin.gov or 608-335-0167

Tim Shively, the Wisconsin Department of Natural Resources (DNR) Forest Health specialist for West Central Wisconsin, will give a presentation titled “Forest Health for Everyone” at a meeting of the Juneau County Men’s Shed at 10 a.m. Tuesday, Jan. 27, in Mauston.

The event is part of a program put on by the Aging and Disability Resource Center of Eagle Country, and will take place at W4890 County Hwy. N, Mauston. It is open to the public. Continue reading “Shively, McNee To Make Public Appearances” →

White Pine Blister Rust Can Devastate Young Stands

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By Tim Shively, DNR Forest Health Specialist
Timothy.Shively@wisconsin.gov or 608-772-6974

A close-up photo of a white pine blister rust canker as seen on a young white pine tree.

A white pine blister rust canker as seen on a young white pine tree. / Photo Credit: Wisconsin DNR

Eastern white pine (Pinus strobus) has historically held great ecological, cultural and economic value throughout Wisconsin, a tradition which continues today. For more than 100 years, however, it has been threatened by a non-native, invasive fungal pathogen called Cronartium ribicola, or white pine blister rust (WPBR).

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