Considered one of the most destructive diseases of conifers in the northern hemisphere, Heterobasidion root disease (HRD) is very difficult to control once established in a forest. Infestation of a conifer stand may significantly impact stand management, making early detection essential.
A Heterobasidion root disease (HRD) fruit body with new white growth observed in the fall. Photo: Wisconsin DNR
Northeastern Wisconsin saw thin and defoliated aspen trees in early summer this year due to a few diseases. A sample from Marinette County turned up Alternaria leaf and stem blight, Venturia leaf and shoot blight and Phyllosticta leaf spot. Venturia was also noted in central Wisconsin, causing shoot blight, which kills the terminal leaders (growth buds) of young aspen.
Aspen crowns were thin due to multiple leaf diseases. Photo: Wisconsin DNR
Red oak trees in many areas of northern Wisconsin are aptly fitting their name as many crowns exhibit a red hue this summer.
Red oaks are producing a second flush of leaves following oak leafroller defoliation in spring, resulting in trees with red-looking crowns. Photo: Wisconsin DNR
Widespread defoliation by oak leafrollers in May and June has led many oaks to generate a second set of leaves after being stripped. New expanding leaves often display a prominent red color that gives the tree crown a stark reddish appearance from afar.
Forest owners and land managers should be on the lookout for beech leaf disease (BLD), a destructive disease of beech trees. The disease is primarily found on American beech (Fagus grandifolia) but can also be found on ornamental species like European, Oriental and Chinese beech (F. sylvatica, F. orientalis and F. engleriana).
Symptomatic striping seen from under the canopy. This photo was taken in Ohio. Photo: Wisconsin DNR
This time of year, you may see black beetles with long antennae flying around, especially in areas with pine trees. These slow, ungainly flyers are a native longhorn species called white-spotted sawyer beetle, also known as pine sawyer.
Scattered white pine in Oneida and Vilas counties had significant amounts of needles that turned light tan or pale yellow this spring. Those needles have mostly dropped from trees, leaving them quite thin.
Tan-colored needles infected with Lophodermium. Photo: Wisconsin DNR
Japanese beetles (Popillia japonica) are an invasive insect that feed on many plant species. They skeletonize leaves, which means that they eat the material between the veins and often leave lacy veins that turn brown and curl.