The Fungi Affecting the October Glory Red Maple

Cankers

• Canker is a general term used to describe a killed area on the bark of a tree, whether it's on the trunk or a branch. Cankers are caused by a variety of fungi, which usually invade injured or wounded areas on the bark, and maples -- including the October Glory -- are among the trees particularly susceptible to them. Many maple cankers are caused by the fungus Eutypella parasitica, which produces perennial cankers. These cankers can cause chronic wounds that leave exposed wood vulnerable to wood-decaying fungi. Whether or not a maple becomes infected with a canker-causing fungi depends on several factors, including the tree's site, health, age, environmental conditions, stress level and cultural practices. Stress caused by drought, insect defoliation, low fertility and herbicide damage makes maples particularly vulnerable to cankers.

Cryptosporiopsis Cankers

• October Glory and "Autumn Flame" maples are the most susceptible to the red Cryptosporiopsis fungus, which causes a canker designated by the same name. This fungus is transferred to the tree by female, narrow-winged tree crickets when they lay their eggs in the bark, creating a 1 mm hole. From this fungus-infected hole, a canker develops. Young cankers are gray, slightly sunken, elongated areas that most often occur on stems less than 10 cm -- or about 4 inches -- in diameter. After a year, the maple usually contains the infection by growing a callus around the canker's margins.

Powdery Mildew

• Maples, including the October Glory, are vulnerable to powdery mildew, a fungal infection of plants that produces white, fluffy growths and tiny black specks on the surface of leaves. The white substance is composed of millions of fungal spores that spread easily on air currents. Because powdery mildew spreads so easily, and many plant species are vulnerable to it, it is highly contagious. Occasional or cool-season infections are not worrisome, but reoccurring or warm-season infections are more severe and can be treated with a wettable sulfur spray.

Verticillium Wilt Resistance

• Verticillium wilt is a potentially deadly fungal infection common in maples and caused by the soil fungus Verticillium dahliae. It can produce a wide range of symptoms, from yellowing and wilting leaves to complete and sudden die off of an entire tree section -- which then quickly progresses to tree death. Most maples are susceptible to verticillium wilt, but October Glory is among the few cultivars that has demonstrated resistance to it, according to the University of Delaware's College of Agriculture and Natural Resources Cooperative Extension. Other red maple cultivars with verticillium wilt resistance include the "Autumn Flame," "Armstrong," "Bowhall," "Scarlet," "Red Sunset" and "Schlessinger."