By Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665
Tubakia leaf spot (Tubakia dryina) is a leaf disease that typically affects the lower canopy of oaks. It caused some issues in 2021 and is affecting red oak trees in north-central Wisconsin this year as well.
Tubakia creates abnormal blotches and spots on oak leaves that can coalesce. Photo: Wisconsin DNR
By Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665
Lecanium scale is popping up in a few areas of Oneida and Vilas counties. These scale insects insert their mouthparts into twigs and suck the sap of the tree. They release honeydew, which can be collected by ants or may coat leaves and anything located under infested trees (i.e., yard furniture or vehicles). Sooty mold can grow on that sticky material and turn things black, so homeowners may want to rinse off the honeydew from outdoor items on a regular basis.
The brown lumps on this stem are lecanium scales. Photo: Wisconsin DNR
By Linda Williams, DNR Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov, 920-360-0665
Have you ever seen an oak wilt fruiting body? Oak wilt is a fungal disease that kills trees in the red oak group (northern red oak, northern pin oak, black oak and other oaks with points on their leaves). Trees in the white oak group (white oak, burr oak, swamp white oak and other oaks with rounded leaves) are more resistant to the disease, but branches or branch tips can still be killed.
Oak wilt pressure pads can create a crack in the bark, allowing beetles to get into the spores. Photo: Wisconsin DNR
Continue reading “On The Lookout For Oak Wilt Fruiting Bodies”
By Michael Hillstrom, DNR Forest Health Specialist, Fitchburg, michael.hillstrom@wisconsin.gov
Typical browning leaf symptoms of red oak trees infected with oak wilt. Photo: Wisconsin DNR
Now is the time to watch for oak wilt! Symptoms typically appear in southern Wisconsin in late June and in northern Wisconsin during July. Watch for browning leaves starting at the top of the canopy and progressing downward. Most leaves will fall from infected trees as they die, typically within two to four weeks.
Several management methods are available to contain oak wilt pockets, so consult your local forest health specialist for guidance on your best options.
The forest health team is also working to evaluate new control methods. Rapid response is currently being tested to more formally evaluate if a new oak wilt infection in a single tree can be stopped before it reaches the roots and spreads to nearby oaks. There is observational data that this method works, but more formal tests are desired. Continue reading “June To October: Oak Wilt Watch!”
By Ethan Wachendorf, DNR Forest Health Lab Technician, Fitchburg, ethan.wachendorf@wisconsin.gov or 608-273-6276
Have you noticed orange, jelly-like growths on cedars this spring? These growths may look like tiny octopus creatures with legs extending all directions, but they’re actually spore horns caused by a fungus.
Orange jelly-like spore horns caused by cedar-apple rust fungus. Photo: Wisconsin DNR
Continue reading “When It Rains, It Spores! Orange Spore Horns Emerge”
By Linda Williams, DNR Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov or 920-360-0665.
White trunk rot (Phellinus tremulae), sometimes called aspen trunk rot, is a fungus that causes decay columns to form in aspen. The fungus enters the tree through branch stubs, wounds or small dead branches that remain on the tree. Perennial conks, or fungal bodies, then grow from these sites.
White trunk rot causes decay in aspen trees. Note the conk (fruiting body) from the fungus on the left side of the pic. Photo: Wisconsin DNR
By Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665 & Paul Cigan, DNR Forest Health Specialist, Hayward, Paul.Cigan@wisconsin.gov, 715-416-4920.
Spring cleanup is always a busy time in the Northwoods as those with second homes and cabins make the trek northward to prepare for a summer of fun. For many, this will mean cleaning up trees and branches damaged by winter storms.
Large white pines (pictured here) and young birch growing on forest edges were most heavily impacted by winter’s storms. Photo: Wisconsin DNR
Continue reading “Spring Cleaning: Storm Damage Cleanup Brings Oak Wilt Risk”
By Michael Hillstrom, DNR Forest Health Specialist, Fitchburg, michael.hillstrom@wisconsin.gov
Black walnut is one of Wisconsin’s healthiest, least threatened tree species. Photo: Wisconsin DNR
Once in a while, the Wisconsin DNR Forest Health Team gets to deliver good news about an emerging insect or disease issue!
Recent research suggests that thousand cankers disease of walnut is not the threat we initially feared when cases appeared for the first time in the eastern U.S. in 2010. Thousand cankers disease is caused by walnut twig beetles carrying a fungal pathogen. The disease has yet to be detected in Wisconsin.
Following its arrival in the eastern United States, the insect’s populations declined. Many stressed urban trees recovered after drought conditions subsided in the impacted areas, and forest trees have fared even better than their urban counterparts. Additionally, walnut twig beetles don’t enjoy Wisconsin winters, as mortality begins in the low single digits Fahrenheit. Perhaps this is why we have not yet found the walnut twig beetle in Wisconsin.
Contact: Paul Cigan, DNR Forest Health Specialist
Paul.Cigan@wisconsin.gov or 715-416-4920
As April brings a high risk of the often-fatal oak wilt disease, the Wisconsin Department of Natural Resources (DNR) recommends not pruning or cutting oaks from April through July.
Do not prune, cut or wound oaks April through July.
Photo: Linda Williams
By Kyoko Scanlon, DNR Forest Pathologist, Fitchburg, Kyoko.Scanlon@wisconsin.gov; and Paul Cigan, DNR Forest Health Specialist, Hayward, Paul.Cigan@wisconsin.gov
Prune oak trees during winter when oak wilt disease-carrying insects are inactive. Photo credit: Wisconsin DNR
It’s pruning season! If your trees need to be pruned, now it the time to do it. Come April, there’s high risk of harmful pests spreading tree diseases such as oak wilt.
Continue reading “Prune Oak Trees In Winter To Help Prevent Oak Wilt”
