Many homeowners are growing concerned about the health of their shade trees due to unsightly leaf browning and leaf drop. The cool, wet weather conditions that we experienced earlier this spring have been conducive for widespread infection by a group of fungal diseases called anthracnose.
Anthracnose diseases are caused by a number of different but closely related fungi. Each anthracnose fungus is specific to the host tree it affects, meaning that the sycamore anthracnose fungus cannot move to other types of plants, such as maples, in the landscape. Anthracnose infections may occur on sycamore, ash, maple, oak, walnut, linden, hickory and other broad-leaved trees.
Symptoms of anthracnose vary from small to large, circular to irregular shaped spots that are tan, dark brown, or black. When immature leaves are infected, they may become distorted. Young leaves may die and fall from the tree. If a severe infection occurs early in the growing season and leaves fall from the tree, a new set of leaves will almost certainly emerge within a period of three to six weeks.
Control of anthracnose with a fungicide application is usually not recommended, although the symptoms are alarming, they rarely if ever lead to the death of the tree. Maintain tree vigor by mulching the root zone of the tree and providing water during dry spells.
Symptoms of ash anthracnose. Photo by Laura Jesse.