By Ethan Wachendorf, DNR Forest Health Lab Technician, Fitchburg, firstname.lastname@example.org 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
Continue reading “White Trunk Rot In Aspen Trees”
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, email@example.com
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.
Continue reading “Thousand Cankers Disease Update”
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
Continue reading “Help Protect Oak Trees From Oak Wilt”
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”
By Todd Lanigan, DNR Forest Health Specialist, Eau Claire, Todd.Lanigan@wisconsin.gov or 715-210-0150
Scattered damage to new red pine shoots has been observed across many counties this summer. With the intermittent rains during the summer, the first thought was that Diplodia shoot blight, a fungal disease, was causing the damage. Upon a closer look, some of the shoot mortality is caused by the red pine shoot moth. From a casual glance, these two problems will look the same, so you really need to take a closer look.
If Diplodia causes the shoot mortality, the shoot usually forms a shepherd’s crook. And, in time, you will find the fungal fruiting bodies on the needles, especially if you look under the needle sheath (covering) at the base of the needles.
Shepherd’s crook caused by Diplodia shoot blight. Photo Credit: Elizabeth Bush, Virginia Polytechnic Institute and State University, Bugwood.org
Continue reading “Diplodia Shoot Blight vs. Red Pine Shoot Moth”
Written by: Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665.
White pine trees in many counties in northeast and northcentral Wisconsin have developed rusty-colored wilting needles on outer branch tips scattered throughout the tree’s crown. These dead branch tips are associated with the feeding by white pine bast scale. The scale is a tiny insect that inserts its straw-like mouthpart into the twig to suck sap from the outer layers of phloem called bast. Damage has been observed on trees over 20 feet tall this year.
Branch tips on this white pine indicate a problem with bast scale and the disease Caliciopsis. Photo Credit: Wisconsin DNR
Continue reading “White Pine Branch Tips Red And Wilting”
Written by: Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665
Oak wilt symptoms are active right now, but so are several other oak issues that may be mistaken for oak wilt symptoms. Issues including Tubakia leaf spot, Botryosphaeria canker, kermes scale damage and mite damage are all causing problems and may be mistaken for oak wilt.
Oak Wilt Leaf Symptoms
Trees in the red oak group (those with points on their leaves) that became infected with oak wilt in the spring will suddenly start to drop their leaves in July and August. Trees that were infected later in the high-risk period (April 15 – July 15 in northern Wisconsin) may start to drop their leaves later, in September or even into October.
Leaves dropping from oak wilt trees can be fully green, tan or a water-soaked, greenish color away from the petiole (leaf stem). There will often be an area that is still green near the petiole, even though the leaf has fallen to the ground. Wilting leaves typically start near the top of the tree and progresses downwards.
Recommended control measures depend on if you have just one tree actively wilting (and no others have died in past years) or if you are dealing with established pockets that have been present for more than a year. Contact your regional forest health specialist to discuss these control options if you think you have oak wilt.
Leaves dropping from trees dying from oak wilt often are brown or water-soaked on the outer portions of the leaf with green still found near the base of the leaf. Photo Credit: Wisconsin DNR
Continue reading “Oak Leaves Turning Brown? There Are Several Reasons This Year.”
By Bill McNee, DNR Forest Health Specialist, Oshkosh, firstname.lastname@example.org or 920-360-0942
Heterobasidion root disease (HRD), formerly known as annosum root rot, was recently found in Fond du Lac and Racine counties for the first time. Thinned pine stands were surveyed by DNR forestry staff in four eastern counties where the disease had not been previously found (Fond du Lac, Manitowoc, Racine and Winnebago counties).
Counties where Heterobasidion root disease (HRD) has been found as of August 2021 are shown in green.
Continue reading “Heterobasidion Root Disease (HRD) Found In Fond Du Lac And Racine Counties”