Disease

New northern oak wilt detections

Posted on by margueriterapp

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

Oak wilt (OW) was confirmed for the first time in Bayfield and Douglas counties and in 16 new northern townships in 2018. The new OW infections occurred on a range of properties, including county, tribal, private, U.S. Forest Service and Board of Commissioners of Public Lands. Wisconsin Department of Natural Resources (DNR) forest health staff are working proactively with affected property managers and landowners to address these infections and prioritize disease prevention and detection in the future.

 

Oak wilt distribution map. Confirmed counties are displayed in red. Confirmed townships are displayed in pink 6-mile square blocks.

The greatest risk of overland transmission in northern Wisconsin is from April 15 to July 15, when fungal spores readily infect open wounds. Most of these new cases occurred during this time frame due to stem and branch damage. The primary causes of damage were roadside brush clearing, pruning, lot clearing and storm-caused branch breakage. Fungal spores may have come from diseased oak firewood and unprocessed wood recently transported into these areas.

Image shows a group of oak trees. Northern red oak on far left is in wilting stage of disease (leaves on but wilting and dropping). Oak on far right has mechanical root collar injury. Dairyland Township, Douglas County.

OW disease center. Oak on far left was infected through belowground root contact with tree damaged in lot clearing (far right). Dairyland Township, Douglas County (photo taken by Paul Cigan).

If oak wilt is present in or within 6 miles of the county where you manage oak, your management activities may be affected by seasonal harvesting restrictions to reduce OW introduction and impact. Read DNR’s oak harvesting guidelines for more information and refer to the list below of new 6 square mile blocks by township and county to see if OW has been detected near your property.

Bayfield County
Barnes T45N R9W
Cable T43N R7W
Drummond T45N R8W
Douglas County
Dairyland T43N R15W
Gordon T44N R11W
Langlade County
Elcho T34N R11E
Langlade T33N R13E
Neva T32N R11E
Sawyer County
Couderay T39N R8W
Hayward T41N R8W
Hunter T40N R7W
Round Lake T41N R8W
Spider Lake T42N R7W
Vilas County
Boulder Junction T42N R6E
Lac du Flambeau T41N R5E, T40N R5E
St. Germain T40N R8E

Please report any suspected oak wilt infections to your local DNR forester or regional forest health specialist and learn more about oak wilt identification and biology on the DNR oak wilt webpage. To learn more about firewood rules and how you can help reduce transmission of pests and diseases, including oak wilt, visit the DNR firewood page.

10 oak leaves lain on downed log display bronze discoloration typical of oak wilt. Midrib and base of leaf are still green.

Bronzed leaves fallen from infected oak. Leaves were observed beneath infected northern red oak. Cable Township, Bayfield County (photo taken by Paul Cigan).

Heterobasidion root disease in Monroe County

Posted on by margueriterapp

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

Heterobasidion root disease (HRD), formerly known as annosum root rot, was recently found in Monroe County for the first time in the town of Little Falls. With this detection, HRD is now known to occur in 28 Wisconsin counties.

HRD distribution map. Counties where HRD is present are shown in blue with most recently confirmed county shown in dark blue.

Fruiting bodies of the pathogen, Heterobasidion irregulare, were found on dead overstory red pine and both live and dead white pine saplings in the Big Creek Fishery Area. The 20-acre stand was a red pine plantation established in 1958 and last thinned in 2012. Wood samples were collected to isolate and identify the pathogen through microscopic identification at the Forest Health Lab in Fitchburg.

Image of multiple spores viewed under microscope. Conidiophores look like Q-tip heads.

Microscopic spores isolated from wood samples and confirmed as HRD in Forest Health Lab.

Based on this new find, a number of townships were added to the 25-mile buffer zones used in determining appropriate management activities according to the HRD Management Guide. There will be a one-year grace period for implementation of the guide in these townships.

The Forest Health Program has records of all confirmed HRD detections. If you suspect this disease is present in a stand, contact your regional forest health specialist.

For more information about HRD, visit the DNR Forest Health webpage.

Public comment period for HRD treatment guidelines revision closes October 16

Posted on by jodieellis

A fruiting body of Heterobasidion irregulare at the base of a pine tree.

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

Wisconsin DNR is seeking public comments on a proposed revision to preventative treatment guidelines for Heterobasidion root disease (HRD). Stand-level HRD treatment guidelines were originally released in 2013. A DNR technical team and stakeholder advisory committee proposed a revised version using recent research findings, operational experience, and economic considerations.

The draft document and information about the public comment process can be found at  https://dnr.wi.gov/news/input/Guidance.html#open through Tuesday, October 16, 2018. All comments must be submitted by that date.

Leaf-browning on white and burr oaks

Posted on by jodieellis

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

Dying leaves on white oak. Photo: Mike Hillstrom.

Dying leaves on white oak. Photo: Mike Hillstrom.

During late August and September of this year, Forest Health staff received several comments about problems with white and burr oaks. Leaves on affected trees turned brown, curled and died prematurely. Some trees were almost completely affected, while others only mildly. Symptoms varied widely between trees, even between those located next to each other. After examining several samples, the DNR Forest Health Lab concluded that damage was likely caused by fungal leaf pathogens and the twig canker fungus Botryosphaeria. Because the damage occurred late in the growing season, afflicted trees will not likely suffer major impacts. Although Botryosphaeria can cause twig dieback, oak trees usually recover without long-term problems. Continue reading “Leaf-browning on white and burr oaks” →

Spruce needle rust not an issue this year

Posted on by jodieellis

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

Orange fruiting bodies of spruce needle rust erupt from needles. From a distance, the tree appears orange due to colored pustules on the needles. Photo: Linda Williams

Orange fruiting bodies of spruce needle rust erupt from needles. From a distance, the tree appears orange due to colored pustules on the needles. Photo: Linda Williams

Occurrences of spruce needle rust in northeastern and north central Wisconsin is low this year for the first time since 2013. Spruce needle rust, caused by the fungus Chrysomyxa weirii, infects spruce needles. Fruiting structures erupt from needles in August in shades of pink, yellow, and orange, greatly affecting the appearance of the trees. In addition, infected needles drop off, causing trees to look sparse.

No treatments are available for already-infected needles. Preventative fungicide treatments for yard trees may be used the following spring and early summer, but treatments must be applied before symptoms appear. Repeated treatments will be necessary; the fungicide, which must fully coat needles to be effective, washes or wears off over time.

Widespread crown dieback and delayed leaf-out of bur oak

Posted on by jodieellis

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

Posted on by jodieellis

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

Posted on by jodieellis
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

Posted on by jodieellis

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.

Continue reading “White pine bast scale and fungus” →

Region-wide needle tip browning on red pine

Posted on by jodieellis
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” →