Disease

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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Tree mortality continues in flooded forests

Mike Hillstrom, forest health specialist, Fitchburg, Michael.Hillstrom@wisconsin.gov, 608-513-7690

Wisconsin has had historically wet weather the last five years, and the impacts to trees are escalating. Forest health staff have noted significant mortality of trees along lakes and rivers from rising water levels. Trees growing in low areas that have not flooded in many years are also being impacted.

Photo of flooded lakeside forest and dead trees around margin of lake.

Rising lake water levels causing conifer mortality.

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Summary of spring 2020 balsam fir mortality event

Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

The sudden balsam fir mortality event in Wisconsin in 2020 was similar to the spring 2018 mortality event, although the mortality this year was more scattered, and fewer trees were killed.

A balsam fir tree with a dead crown that has retained its needles.

Trees that died suddenly this spring retained their needles, which turned reddish-brown to brown.

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Oak webworms, blotchminers, skeletonizers and dead branch tips in late summer

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

If you’ve ever looked closely at oak leaves in late summer you know that you can find lots of interesting things on them this time of year. You’ll see anything from a variety of caterpillars and galls of all shapes and sizes to dead portions of branches caused by insects and diseases. These late season defoliators rarely cause actual health issues for the tree, and rarely require any control, but they can be very noticeable with some dramatic damage. Continue reading “Oak webworms, blotchminers, skeletonizers and dead branch tips in late summer”

Be on the lookout for beech leaf disease

By Elly Voigt, forest health lab assistant, Fitchburg

Beech leaf disease (BLD) is a relatively recently discovered, destructive disease of beech trees in the US. It was first observed in 2012 in Ohio and has since spread to areas of Pennsylvania, New York, Connecticut, Rhode Island, Massachusetts and Ontario, Canada. BLD affects our native beech species, American beech (Fagus grandifolia) and ornamental beech species, including European beech (Fagus sylvatica). The disease has not yet been observed in Wisconsin but could become an issue in the future.

Overhead view of beech leaves show puckering of leaf segments.

Symptomatic leaf puckering of a beech tree with BLD. Credit: Ohio State University.

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Interactive HRD stump treatment guidelines available online

The HRD stump treatment guidelines are now available in an interactive format to make it easier to obtain stand-specific recommendations. You can find the link called “Interactive guidelines” on the right side bar under “Additional Resources” at the DNR HRD webpage. The user will be asked a series of questions and then a stand-specific recommendation will be provided at the end. The interactive guidelines incorporate Exceptions and Modifications described in the guidelines. Check it out!        

Chlorosis: common causes and next steps in management

Mike Hillstrom, forest health specialist, Fitchburg, Michael.Hillstrom@wisconsin.gov, 608-513-7690

Chlorosis, which is marked by yellow leaves with green veins, is a common tree and shrub issue in Wisconsin. It is often a result of a nutrient deficiency of iron and manganese. 

A chlorotic leaf has yellow leaf tissue with green veins.

A chlorotic oak leaf displays yellow leaf tissue with green veins.

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Report surviving elm in the forest

You can help keep native elm trees in the forests of Wisconsin! The US Forest Service continues to work on a project to identify Dutch elm disease (DED)-tolerant American elms native to Wisconsin forests. The goal of the project is to identify and propagate survivor American elms, especially from the colder hardiness zones 3-4, and develop a series of clone banks. Selections would eventually be screened for tolerance to DED. Ultimately, the goal is to make DED-tolerant American elm available for reforestation in northern areas, particularly as a component on sites currently forested by black ash.

If you live in hardiness zones 3 and 4, please look for evidence of surviving elms and report them to the US Forest Service.

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