Northeast WI Forest Health

Professionally-designed HRD guidelines now available

Cover page of HRD guidelines documentThe professionally-designed version of the Heterobasidion root disease (HRD) stump treatment guidelines is now posted on the DNR’s HRD webpage. The revised stump treatment guidelines, developed to reduce the risk of introduction and spread of HRD in Wisconsin, were implemented January 1, 2019. The content is the same as the guidelines that were approved last year, but this document has a layout that is much more user-friendly. Explore the new look of the HRD guidelines.

 

Watch for signs of oak wilt

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

Trees in the red oak group (those with points on their leaves) that were infected with the oak wilt fungus this spring will rapidly drop their leaves from July to September and be dead by fall. This wilting and dropping of the green leaves happens quickly. Once it starts, the tree will drop most of its leaves within just a few weeks.

Tree dying from oak wilt with rapidly dropping leaves.

Tree dying from oak wilt with rapidly dropping leaves. The tree was injured in May, attracting the beetles that help spread the fungus, and the tree was dead by the end of the year. Photo was taken in August.

Red oak leaf from infected tree. Leaves are often green at the base, with the outer portions of the leaf appearing water-soaked or brownish.

Red oak leaf from infected tree. Leaves are often green at the base, with the outer portions of the leaf appearing water-soaked or brownish.

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Ants, aphids and sooty mold on white pine

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

Ants, aphids, and sooty mold can cause stunting and death of young white pines, but fortunately there are some steps you can take to protect your trees from these pests.

Ants guard aphids from predators as they feed. In exchange, the ants collect the sweet honeydew excreted by the aphids.

Ants (upper right) guard aphids from predators as they feed. In exchange, the ants collect the sweet honeydew excreted by the aphids.

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Heavy seed crop leads to sparse-looking trees

Todd Lanigan, forest health specialist, Eau Claire, Todd.Lanigan@wisconsin.gov, 715-839-1632

You may have noticed some of the elms and maples had a lot of brown in them at the end of May and early June. Some elms and maples produced a lot of seed this spring, which reduced the amount of energy available for producing leaves. With fewer leaves and more of the brown, papery seeds, the trees can take on a thin, brown appearance.

Heavy seed years can occur for many reasons. It happens naturally from time to time and it can also be stimulated by environmental stressors. A couple of examples of environmental stressors are: excessive moisture, winter injury and frost damage to roots.

The cause of this year’s heavy seed production is anyone’s guess. There does not appear to be a common pattern between the affected trees to indicate whether it was simply a normal heavy seed year or related to an environmental factor.

 

Browning on tamarack needles

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

Defoliation from larch casebearer (Coleophora laricella) is showing up in some areas of northeast and northcentral Wisconsin. The defoliation is patchy and of moderate intensity, resulting in trees with various degrees of browning due to the insect’s feeding habits. Some appear pale yellow or brown throughout the crown while others only have partial browning.

Defoliated larch needles turn yellow then brown.

Defoliation by larch casebearer will cause needles to turn yellow then brown. Trees will usually send out more needles and be green again by mid-summer.

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Branch flagging caused by jack pine resin midge

Paul Cigan, forest health specialist, Hayward, Paul.Cigan@wisconsin.gov, 715-416-4920

Jack pine shoots are flagging over a large area of northern and west central Wisconsin this summer due to feeding injury from the jack pine resin midge. Symptoms include scattered dead branch tips and pitch masses on terminal buds and on twigs where larvae feed.  

Jack pine with dead branch tips caused by jack pine resin midge. Photo: Paul Cigan.

Jack pine with dead branch tips. Photo: Paul Cigan.

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Native caterpillars not a major concern for trees

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

Eastern tent caterpillars (ETC) are hatching and beginning to feed on host trees, including cherry, apple and crabapple. Landowners and homeowners may notice the white silken tents forming in branch forks. Although they form unsightly tents, ETC is a native insect so management is not typically necessary. Even completely defoliated trees will put out new leaves within a few weeks.

A group of eastern tent caterpillars warm themselves on white silk tent before leaving to feed on black cherry leaves.

If landowners want to remove the tents the best time to do so is early morning or evening when the caterpillars are inside. Unless it is raining, eastern tent caterpillars leave their tents each morning to feed throughout the day before returning at night. Caterpillars can be removed either by hand if they are within reach or with a rake if they are high in the tree. They can then be killed by soaking them in soapy water or sealing them in a trash bag. Insecticides are rarely necessary but should penetrate inside the tent if used. Do not prune branches, burn tents or soak them with WD-40. These methods are more harmful to the tree than ETC defoliation and are not recommended.

For more information on eastern tent caterpillar, read this factsheet from UW-Madison Division of Extension.

Protect yourself from ticks and tickborne illnesses

Bill McNee, forest health specialist, Oshkosh, Bill.McNee@wisconsin.gov or 920-360-0942

Adult deer tick. Credit: Scott Bauer, USDA Agricultural Research Service, bugwood.org.

So far this spring we are off to a busy tick season, with many reports and photos being sent in to DNR staff. Ticks can be found year-round in Wisconsin but are most active from May to September. Some species, including the deer tick responsible for Lyme disease, carry infectious diseases that elevate them from mere nuisance to serious health threat.  Lyme disease is most often spread by very small, immature ticks known as “nymphs.” Adult deer ticks can also transmit Lyme disease, but because they are larger, they are more likely to be discovered and removed compared to the tiny nymphs which can be as small as a chia or sesame seed.

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Needle and leaf diseases are back!

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

It’s nearly summer and the usual cast of disease characters are on the scene following wet spring conditions. Rhizosphaera needlecast and other needle diseases impacting spruce continue to be a major concern for landowners and homeowners. Diseases in hardwoods are also popping up. For more information on needle and leaf diseases affecting trees in Wisconsin and resources to learn more, click below to read full article. 

A row of spruce trees with dead branches and missing needles caused by Rhizosphaera needlecast.

Spruce trees impacted by Rhizosphaera needlecast.

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Branch tips littering the ground under your trees?

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

Have you been noticing branch tips scattered on the ground beneath spruce, fir or pine trees this spring? You may be seeing one of a few things – damage from small animals or breakage caused by the harsh winter we had. Fortunately, the damage from either is unlikely to do serious harm to your trees. 

Spruce branch tips found on ground were clipped from tree by squirrels.

Spruce branch tips found on ground were clipped from tree by squirrels.

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