Author: jodieellis

Oak leaves dropping (but not from oak wilt)

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

Heavily-spotted oak leaves began to drop in early August. Spots appeared on both the front and back of leaves. Photo: Linda Williams

Heavily-spotted oak leaves began to drop in early August. Spots appeared on both the front and back of leaves. Photo: Linda Williams

Last year, Forest Health News published an article about oaks prematurely dropping leaves although they were not infected by the fungal pathogen Ceratocystis fagacearum, the cause of oak wilt disease. Oak trees infected with oak wilt disease in springtime rapidly wilt and drop green leaves in July or August. However, oak wilt disease is not the only reason oak trees prematurely drop leaves. Continue reading “Oak leaves dropping (but not from oak wilt)”

Tree decline and mortality observed at many wet sites this summer

By Bill McNee, DNR Forest Health Specialist, Oshkosh. bill.mcnee@wisconsin.gov; 920-360-0942

An aerial view of tree mortality in very wet areas. Photo: Bill McNee

An aerial view of tree mortality in very wet areas. Photo: Bill McNee

Site visits and aerial surveys conducted on trees in eastern Wisconsin by the Wisconsin DNR forest health team in July and August found multi-species decline and mortality common at many very wet sites. Continue reading “Tree decline and mortality observed at many wet sites this summer”

Oak leaf fold galls and itch mites

by Mike Hillstrom, forest health specialist (Fitchburg). Michael.Hillstrom@wisconsin.gov;
208-513-7690

Oak leaf fold galls on red oak leaves. Photo: Mike Hillstrom

Oak leaf fold galls on red oak leaves. Photo: Mike Hillstrom

Ethan Lee, parks supervisor for the City of Janesville, recently reported symptoms of oak leaf fold galls on an oak tree on the University of Wisconsin – Rock County campus. Oak leaf fold galls, caused by fly larvae, are generally harmless to trees. However, new information links oak leaf galls with a recent invasive mite from Europe, Pyemotes herfsi, commonly called the oak leaf itch mite. Although no evidence of itch mite was found on the affected red oak tree, more than 50% of the tree’s leaves contained leaf fold galls. Continue reading “Oak leaf fold galls and itch mites”

Aspen blotch miner caterpillars

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

The tops of aspen leaves will appear off-colored when aspen blotch miner caterpillars feed within.

The tops of aspen leaves will appear off-colored when aspen blotch miner caterpillars feed within. Photo: Linda Williams

If you’ve noticed aspen trees seem a little pale lately, you are probably seeing damage from aspen blotch miner caterpillars. Typically, these leaf-mining insects only affect young aspen trees, but this year I’ve found uniform damage on bigger trees with large crowns. Symptoms include thinned crowns, off-color leaves with blisters on their undersides, and, later in the summer, curling and browning leaves. Tiny caterpillars spend their entire lives feeding within the leaf; they then pupate into the tunneled-out areas. Moths emerge in August and spend the winter in protected places.

I have reported this insect each year since 2012 in northeastern Wisconsin. This year, there were aspen leaf blotch miners in Marinette, Florence, Forest, Oneida, and Vilas counties, which is similar to where they were found last year. Although defoliation can be severe, aspen trees usually tolerate the situation well. Many affected aspen trees will send out new leaves after feeding by caterpillars ends. Although damage may appear severe, the effects on the trees’ overall health seems negligible.

 

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.

Continue reading “Widespread crown dieback and delayed leaf-out of bur oak”

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, Pennsylvania, New York and Ontario. Its cause is not yet known.

Continue reading “Be on the lookout for beech leaf disease”

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”

Defoliation of black cherry trees by cherry scallop shell moth

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

Caterpillars of cherry scallop shell moths (Rheumaptera prunivorata) are defoliating black cherry trees of all sizes in far southeastern Jefferson County and slightly into Walworth County. Many cherry trees have been completely defoliated. This is the third consecutive year of damage in this location. Defoliation by cherry scallop shell moth caterpillars has increased each year; hopefully natural enemies that typically cause the populations to crash show up soon and do their job as multiple years of defoliation is stressful to trees. In addition to cherry scallop shell moths, there is concern about possible attack on black cherry trees by peach bark beetles (Phloeotribus liminaris), but none have been reported yet.

Continue reading “Defoliation of black cherry trees by cherry scallop shell moth”

Fall webworms start making an appearance

By Todd Lanigan, forest health specialist, Eau Claire, WI. Todd.Lanigan@wisconsin.gov; 715-210-0150

A silken nest full of caterpillars, excrement and debris. Photo: Todd Lanigan

A silken nest full of caterpillars, excrement and debris. Photo: Todd Lanigan

Web-like nests of fall webworm (Hyphantrea cunea) caterpillars, a common native pest active from July through September, are beginning to appear in parts of the state. A common native pest throughout most of the U.S. and southern Canada, fall webworm caterpillars feed on leaves of almost all shade, fruit, and ornamental trees and shrubs, except for conifers. They typically form nests of loose webbing over the tips of tree branches.  Although populations of fall webworm caterpillars are rarely large enough to cause lasting damage to trees, the presence of nests and feeding damage from caterpillars can greatly affect trees’ aesthetic value. Typically, trees recover from feeding damage on their own, but defoliation for more than two or three years in a row could make trees more susceptible to diseases and pests.

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Forest Health Program welcomes new forest invasive plant coordinator

By Jodie Ellis, communications specialist, Madison. Jodie.Ellis@wisconsin.gov; 608-843-3506

Michael Putnam

Michael Putnam, DNR Forestry’s new forest invasive plant coordinator.

The Forest Health Program is excited to welcome Mike Putnam as its new forest invasive plant coordinator. Mike has been working with the program as an LTE for more than four years in Madison; his new position is in Rhinelander. He’ll be focusing on invasive plants prevention and management with DNR foresters and partners, so please reach out to him with field work opportunities.

Continue reading “Forest Health Program welcomes new forest invasive plant coordinator”