Disease

Widespread crown dieback and delayed leaf-out of bur oak

by Paul Cigan, forest health specialist, Hayward, Paul.Cigan@wisconsin.gov. 715-416-4920 and Todd Lanigan, forest health specialist, Eau Claire, Todd.Lanigan@wisconsin.gov, 715-210-0150

Typical appearance of bur oak with crown dieback associated with cynipid gall wasp infestation in northwest WI during early summer, 2018.

Bur oak showing moderate crown dieback. Photo: Paul Cigan

Bur oak with heavy crown dieback and delayed leaf flushing in Polk County.

Bur oak with severe crown dieback. Photo: Paul Heimstead

Widespread dieback of twigs and branches and delayed leaf-out were present on bur oak trees this spring in Barron, Burnett, Chippewa, Eau Claire Polk, Rusk, and Sawyer counties, and in parts of central and east central Minnesota. Crown dieback of between 10 – 50% was observed in both mature and sapling-sized trees, although it was more common on open-grown trees and those along woodland edges. Tufted or “broomed” leaf shoots were apparent, a result of epicormic shoots developing below dead twigs and branches. Most impacted trees recovered well by early July as crowns filled in with leaves and epicormic shoots. Leaves in recovered trees appeared generally healthy and normal-sized.

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Be on the lookout for beech leaf disease

By Kyoko Scanlon, forest pathologist, Fitchburg. Kyoko.Scanlon@wisconsin.gov; 608-235-7532

Early striping from BLD as seen looking up into the canopy. Photo: The Ohio State University.

Early striping from BLD as seen looking up into the canopy. Photo: The Ohio State University.

Although beech leaf disease (BLD) has not been found in Wisconsin, forest owners and managers should keep an eye out for it on American (Fagus grandifolia) and, to a lesser extent, European (Fagus sylvatica) beech trees. Beech leaf disease is becoming a serious issue in parts of Ohio, West Virginia, Pennsylvania, New York and Ontario. Its cause is not yet known.

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Balsam fir mortality in many counties around the state

Counties shaded in blue are where balsam mortality has been reported, but the is even more widespread than this map indicates.

Counties shaded in blue are where balsam mortality has been reported, but it is even more widespread than this map indicates.

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665 and Paul Cigan, forest health specialist, Hayward Paul.Cigan@wisconsin.gov, 715-416-4920

Reports of balsam fir suddenly turning rusty red to brown and dying have been coming in steadily this spring and summer. The accompanying map shows where this has been reported so far this year.

Spoiler alert! There are no insect or diseases involved. It appears the cause may be unusually severe winter drying or winter damage.

Continue reading “Balsam fir mortality in many counties around the state”

White pine bast scale and fungus

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

Branches in the mid- and lower-crown of this white pine are being killed by white pine bast scale and a fungal disease.

Branches in the mid- and lower-crown of this white pine are being killed by white pine bast scale and a fungal disease. Photo: Linda Williams

White pine bast scale and canker fungus has been identified in two sites in Oneida County. This insect/fungus complex is a new issue in the state; those who work with white pine should be alert for signs and symptoms.

White pine bast scale, a native scale, is tiny, black, oval-shaped, and lacks both eyes and legs. It uses a long stylet to siphon sap from outer layers of phloem (bast) of twigs and branches. White pine bast scales live under lichens on white pine branches. Although lichens don’t directly harm trees, they provide shelter for scale insects.

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Region-wide needle tip browning on red pine

Typical appearance of needle tip browning on lower portion of red pine crowns

Red pine with needle tip browning on the lower crown. Photo: Paul Cigan

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

Although no tree mortality is associated with the condition, widespread needle tip browning on red pine has been observed for the second consecutive year across much of the upper Great Lakes region. The condition is heavier in some places than others, but once in a stand or location, tends to be evenly distributed. Needle tip browning is common on the lower half of mature red pine crowns. On two- to three-year-old needles, the outer half to three-quarters of the needles appear reddish brown to straw-colored while needle bases remain green. Black or dark brown necrotic bands and spots are often present on symptomatic needle tips. Lower crown thinning is also common on symptomatic pine. Newly impacted needles will gradually lighten in color from reddish brown to straw-colored as dead needle tips dry out through the growing season. Continue reading “Region-wide needle tip browning on red pine”

Rhizosphaera needle cast disease on spruce

Spruce trees affected by rhizosphaera needle cast disease will have thin foliage in the lower parts of the tree, and branches may die in severe cases. Some trees are more susceptible, like the tree on the far left and the tree on the far right.

Spruce trees affected by rhizosphaera needle cast disease will have thin foliage in the lower parts of the tree, and branches may die in severe cases. Some trees are more susceptible, like the tree on the far left and the tree on the far right. Photo: Bethany and J.R. Pulham

By Linda Williams, forest health specialist, Woodruff.  Linda.Williams@wisconsin.gov; 715-356-5211 x232

 Are the lower branches of your spruce tree suddenly looking very thin? Rhizosphaera needle cast disease, caused by a fungal pathogen, can severely impact spruce, killing needles and causing them to drop prematurely. Wet years such as 2017 are great for the fungus, but bad for trees. Spring 2016 was also unusually wet, allowing the fungus to start to build up. With all the rain and wet conditions of 2017, the disease exploded. Continue reading “Rhizosphaera needle cast disease on spruce”

New “Tick App” available

Ticks pose increasing health threats throughout North America

Ticks pose increasing health threats throughout North America. Photo: WI DNR

from the May 2018 edition of RECReport, for the WI DNR Bureau of Parks and Recreation Management

The University of Wisconsin-Madison, a partner in the Midwest Center of Excellence (Center) in Vector-Borne Diseases, has announced that “Tick App” is now available for download. Tick App is a phone application that is part research tool and part educational tool with the goal to transition towards a preventative tool over time.

The Center would like to enroll people, by the app, in their study to determine the risk for tick encounters, assess the success/failure of self-reported prevention strategies, and educate people at the same time. Participation is entirely voluntary. When people download the app, they will go through a sign-up process—and about 5 minutes of questions—so the researchers can assess risk factors for tick exposure.

When people are in the app they can complete daily tick diaries (asking about activities and tick exposure) and can report a tick. Users can even send in an image for identification after the report is completed. For more information on the Tick App, visit http://www.thetickapp.org or tickapp@wisc.edu.

White pine blister rust

On this white pine, you can see on the lower left a branch recently killed by blister rust; on the lower right is a branch that is slightly off-color. The off-color branch also had a canker but it had not yet completely girdled the branch.

On this white pine, you can see on the lower left a branch recently killed by blister rust; on the lower right is a branch that is slightly off-color. The off-color branch also had a canker but it had not yet completely girdled the branch. Photo: Linda Williams

By Linda Williams, forest health specialist, Woodruff. Linda.Williams@wisconsin.gov; 715-356-5211 x232

White pine blister rust is a fungus that causes cankers on white pine. The cankers can girdle and kill branches or the main stem of the tree. White pine blister rust infections create “dead spots” or cankers that continue to expand each year on the branches or main stem. Eventually, orange pustules develop which erupt around the edges of the canker; this is how the fungus reproduces. Continue reading “White pine blister rust”

How are communities handling EAB across Wisconsin?

The Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP) has recently issued a statewide quarantine for emerald ash borer (EAB), regulating the pest in Wisconsin. Since the menace has already affected 48 of Wisconsin’s 72 counties, many municipalities have been acting on EAB management plans they set into place, including the City of Racine and Ozaukee county have been managing the pest.

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Protect oak trees from oak wilt by waiting until after July to prune

By Don Kissinger, DNR urban forester (Wausau), Don.Kissinger@wisconsin.gov, 715-359-5793 and Paul Cigan, DNR forest health specialist (Hayward), Paul.Cigan@wisconsin.gov, 715-416-4920

To protect oak trees and help prevent oak wilt, the Wisconsin Department of Natural Resources advises people to avoid pruning oaks on their property from April through July.

Spring and early summer pruning makes oak trees vulnerable to oak wilt, a fatal fungal disease that rapidly kills trees in the red oak group and weakens those in the white oak group. Any tree damage during this time creates an opening that exposes live tree tissue and provides an opportunity for the oak wilt fungus to infect the tree.

The red oak group includes northern pin oak, northern red oak, red oak and black oak; the white oak group includes bur oak, swamp white oak, white oak and English oak.

Pin oak (Quercus palustris)

Pin oak (Quercus palustris)
Photo: Gary Fewless, University of Wisconsin, Green Bay

“It takes only a few minutes for beetles that carry oak wilt spores to land on a fresh wound and infect your tree,” said Paul Cigan, DNR forest health specialist in Hayward.

Property owners with oak trees are encouraged to check with their municipality to find out if there are local oak wilt ordinances which may have different pruning restrictions.

The use of tree paint or a wound dressing is not normally recommended on pruning cuts or wounded surfaces on most trees. But for damaged oaks, the use of such products are suggested from April through July. An immediate light painting of wounds or cuts on oak trees during this time helps protect against the spread of oak wilt by beetles.

Don Kissinger, a DNR urban forester in Wausau, said there are also other important reasons to avoid pruning many kinds of deciduous trees in spring beyond concerns about oak wilt.

“Spring is the time when tree buds and leaves are growing, leaving the tree’s food reserves low,” Kissinger said. In general, the best time to prune trees is in winter.

Oak wilt and other diseases move easily on or in firewood logs year-round. To protect trees in general, don’t move firewood long distances, or only use firewood labeled as Wisconsin-certified.

As of January 31, 2018, oak wilt has been found in all Wisconsin counties except Douglas, Bayfield, Ashland, Iron, Forest, Taylor, Door, Kewaunee, Calumet, and Manitowoc counties. Several of these counties contain the highest abundance of healthy and productive oak forests in the state. Taking recommended precautions with living oak trees and keeping firewood local to prevent the spread of oak wilt will help keep them that way for years to come.

More information is available online at the WI DNR website, including a recently released video on oak wilt. Visit the DNR website, https://dnr.wi.gov/, and search for “oak wilt” or “firewood.” Additional information about proper pruning techniques is available from community foresters or by searching for “tree pruning.”