What is that?

• Anthracnose is a leaf disease caused by fungi that are active in the early spring.
• It can highly disfigure leaves on susceptible trees, and this very noticeable damage often concerns homeowners greatly, especially in the spring.
• Shade tree anthracnose is separate from dogwood anthracnose, which is a different disease caused by a much more virulent fungus that requires early and aggressive management.

• Fungi of the genus Discula (and related forms) are responsible for this disease.
• The fungi pass the winter on dead leaves on the ground, or occasionally in cankers on affected twigs in the trees. In the early spring, their spores are dispersed for reinfection.
• Anthracnose fungi can only affect leaves under cool and moist conditions typical of early spring. When the weather warms up and dries out, infection can not occur.

• The symptoms include irregular, brown-black blotches, sometimes paralleling the leaf veins.
• When the weather is particularly favorable (lengthy cool and moist period), entire leaves can become blighted and significant tree defoliation can occur.
• Some important landscape and street trees are particularly susceptible. They include maples, ashes, sycamores, beech, birch, elm, walnut, and horsechestnut.

• This is a minor blemish that rarely affects the overall health of the tree.  Since this disease will stop as the weather becomes warmer and drier, there is no need for control measures in most cases.
• Even if defoliation occurs, the tree will put out its second flush of growth under warmer and drier conditions that prevent reinfection by the fungus.
• To help reduce the infection level the following spring, remove and discard the leaves from a diseased tree in the fall-- or compost them properly.
• If anthracnose is serious near a new planting site, select trees that are resistant to it.
• Fungicides are rarely recommended. 
• If anthracnose is a recurring problem and/or the tree is on a prominent site, where the damage is esthetically unacceptable, a fungicide program may be warranted.
• Initiate any fungicide treatment before budbreak; by the time symptoms can be seen, it is too late to treat the fungus. Check your local University Extension office for recommendations on products, dosage, and timing.