Disease

Protect Oak Trees From Oak Wilt By Pruning After July, Not Before

By Don Kissinger, DNR Urban Forester, 715-348-5746 or Don.Kissinger@wisconsin.gov; Paul Cigan, DNR Forest Health Specialist, 715-416-4920 or Paul.Cigan@wisconsin.gov

The Wisconsin Department of Natural Resources (DNR) urban and forest health specialists recommend not pruning or cutting oaks from April through July to protect oak trees from the often fatal oak wilt disease.

The spring season often draws property owners outdoors to soak up rays of long-awaited sunlight, breathe in some fresh air and begin seasonal yard maintenance and cleanup projects. While spring is a time to dust off yard tools like rakes, shovels and weed clippers, when it comes to the health of oak trees, keeping those chainsaws and trimming tools a safe distance away will go a long way to ensure that your trees stay healthy for many more spring seasons to come.

Sap-feeding beetle on a diseased oak tree in Sawyer County.

Sap-feeding beetle on a diseased oak tree in Sawyer County.

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Stalactiform Stem Rust Of Jack Pine

By Todd Lanigan, DNR Forest Health Specialist, Eau Claire. Todd.Lanigan@wisconsin.gov or 715-210-0150

Stalactiform stem rust, which occurs in the Lake States and Canada on jack pines, was recently found in western Monroe County. Before this discovery, the only place I have seen stalactiform stem rust in Wisconsin was Adams County in the mid to late 1990s.

Rust diseases can be identified by the galls’ shape and location and by cankers present on the trees. On jack pine seedlings and saplings, stalactiform stem rust can cause elongate swellings on branches or the main stem (trunk).

A jack pine with stalactiform stem rust galls that squirrels have chewed on

A jack pine with stalactiform stem rust galls that squirrels have chewed on.

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New Oak Wilt Vectors Emergence User Interface Available Online

By Kyoko Scanlon, DNR Forest Pathologist, Kyoko.Scanlon@wisconsin.govor 608-235-7532 and Elly Voigt, DNR Forest Health Communications Specialist and Lab Technician, Eleanor.Voigt@wisconsin.gov or 608-273-6276

Oak wilt is a serious disease that occurs when insects carrying oak wilt fungal spores land on a healthy oak tree’s fresh wound. To prevent oak wilt infections, it is important to avoid pruning, wounding and harvesting oaks when these insects are abundant, generally April through July.

Predicting exactly when these insects start to emerge in the spring can be difficult as their emergence is highly weather-dependent, and spring weather varies significantly from year to year.

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Oak Wilt Vectors Emergence User Interface Now Available

By Kyoko Scanlon, Forest Pathologist, Kyoko.Scanlon@wisconsin.gov or 608-235-7532 and Elly Voigt, Forest Health Communications Specialist and Lab Technician, Eleanor.Voigt@wisconsin.gov

Oak wilt is a serious disease of oaks that spreads to new areas when insects carrying oak wilt fungal spores land on a fresh wound of a healthy oak tree. To prevent oak wilt infections, it is important to avoid pruning, wounding and harvesting of oaks when these insects are abundant.

Predicting when these insects emerge in spring can be difficult as their emergence is highly weather-dependent and spring weather varies significantly year to year. The good news is that a new online interface is now available to provide users with localized information about the emergence status of the two most important insects that transmit oak wilt in Wisconsin. Because the interface uses a degree-day model constructed from insect trapping data and actual weather data, it is useful to refine the beginning of the periods when pruning, wounding and harvesting of oaks should be avoided.

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Join Virtual Q&A Sessions With DNR Experts

The Wisconsin Department of Natural Resources (DNR) Urban Forestry program will have a virtual booth at the 2021 WAA/DNR Urban Forestry Annual Conference, Feb. 21-23, 2021. Our virtual booth will feature a new video on our grant program and live group Q&A sessions with our grant and forest health specialists.

A virtual booth could be described as a hybrid between a Zoom call and a website, with some additional features. If you’re attending the annual conference, you’ll have the opportunity to stop by our virtual booth, just as you would at an in-person meeting. Staff will be available to answer questions at set times, and there will be resources available to view and download.

A new video on our DNR Urban Forestry Grant program will be available to view in the booth throughout the conference. Created by DNR Finance Specialist Nicolle Spafford and DNR Grant Manager Chase O’Brien, the video will show you the program’s basics and inspire you to start projects of your own while seeing some successful programs across the state.

Join One Of These Live Q&A Sessions At Our Virtual Booth

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Revised Factsheets, Guidelines Now Available

By Elly Voigt, DNR Forest Health Lab Technician and Communications Specialist, Eleanor.Voigt@wisconsin.gov

The Wisconsin Department of Natural Resources (DNR) has just released several updated publications, including the annual update of the Heterobasidion root disease and oak wilt factsheets and guidelines. Updated versions can be found on the DNR’s forest health webpage by clicking the links below:

     – Heterobasidion root disease factsheet
     – Heterobasidion root disease guidelines
     – Oak wilt factsheet
     – Oak harvesting guidelines

Minor revisions were also made to the environmental cause of tree damage and conifer bark beetle factsheets. Visit the DNR webpage here for other forest health publications.

For more information on forest health, visit the DNR webpage, or talk to your regional Forest Health Specialist.

Wisconsin DNR 2020 Forest Health Annual Report

By Elly Voigt, DNR Forest Lab Technician and Communications Specialist, Eleanor.Voigt@wisconsin.gov

The cover page of the 2020 Annual ReportThe Wisconsin Department of Natural Resources’ Forest Health team recently completed the 2020 Forest Health Annual Report. The report summarizes impacts from pests, diseases and weather on the health of Wisconsin’s forests. Highlights from 2020 include:

• An update on emerald ash borer in Wisconsin, including newly confirmed counties
• New township detections of oak wilt
• Flooding and tornado damage
• Summary of state nursery studies

For access to the report, visit the link here.

How to look for white pine bast scale and Caliciopsis canker

By Elly Voigt, DNR Forest Health Communications Specialist and Linda Williams, DNR Forest Health Specialist, Linda.Williams@wisconsin.gov, 920-360-0665

The association between a tiny insect and an inconspicuous fungus is causing branch and sapling mortality. White pine bast scale (WPBS; Matsucoccus macrocicatrices) and Caliciopsis canker (caused by Caliciopsis spp.) are agents in an insect/disease complex impacting white pines (Figure 1).

A white pine tree showing branch dieback in the mid and lower crown.

Figure 1. Branch mortality caused by WPBS and Caliciopsis canker.

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Phomopsis galls

By Elly Voigt, DNR Forest Health Lab Technician and Communications Specialist, Eleanor.Voigt@wisconsin.gov

Galls are woody swellings on the branches or trunk of a tree and can be caused by insects or fungi. Winter and early spring are the best times to notice galls thanks to bare branches. One type of gall, caused by Phomopsis fungi, occurs on northern red oak, hickory, maple and several other tree species.

Numerous woody galls on the branches of an oak tree.

Phomopsis galls on the branches of an oak.

There will frequently be many phomopsis galls on one tree while nearby trees are completely unaffected, probably due to individual resistance differences. While small phomopsis galls have minimal effects on trees, larger galls can girdle branches, causing branch dieback. Galls grow very slowly, and many heavily affected trees survive for decades, even with a large gall on their trunk.

There are currently no treatment recommendations for Phomopsis galls, but you can prune and dispose of affected branches. Many landowners choose to let them be.

Deer hunters should avoid ash trees when placing deer stands this hunting season

By Bill McNee, forest health specialist, Oshkosh, bill.mcnee@wisconsin.gov, 920-360-0942

This November, hunters should avoid placing tree stands in or near ash trees, especially in the southern half of Wisconsin, Door County and the Mississippi River counties. Most ash trees in these areas are dead or dying from infestation by emerald ash borer (EAB) and may unexpectedly snap or drop large branches. Place deer stands in non-ash trees to keep yourself safe from infested ash this hunting season.

Infographic showing four ways to identify ash trees.

A photo guide to identifying ash trees.

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