Disease

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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New insect and disease factsheets available

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

The forest health team has produced four new factsheets since the start of 2020. These resources are designed to be informative, 2-page documents for a wide audience that includes landowners, foresters and natural resource professionals, educators, and more. The new factsheets of 2020 are linked below, and more will be announced as they are finalized:

Please check them out and our other recently updated factsheets about Heterobasidion root disease, oak wilt, conifer bark beetles, and hickory decline and mortality. You can find all of these and more forest health publications in the publications catalogue and on the DNR forest health webpage.

What’s that orange goo?!

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

What’s the orange goo on that tree?!

Should I fight or should I flee?

I bet forest health staff can ID!

Close-up of orange gelatinous gall growing on cedar caused by cedar apple rust.

The spore-producing, slimy, orange gall caused by cedar apple rust fungus.

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Pine tortoise scale can cause branch and tree mortality, sooty mold problems

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

Pine tortoise scales are sometimes found at very heavy densities on jack and scotch pine twigs. In Wisconsin they prefer young jack pine trees, inserting their straw-like mouthparts into twigs and sucking out the sap. When populations are high, pine tortoise scale can cause branch mortality and even whole tree decline.

Tiny pine tortoise scales clustered on a pine branch tip.

Pine tortoise scales are so plentiful on this twig that they are practically on top of one another.

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