How to detect Anthracnose in Maple and Oak Trees
Anthracnose is a fungi that affects many plants and trees. Each species reacts slightly different, and the symptoms and outward signs of Anthracnose vary from plant to plant. It is a foliage disease that can affect shade trees, but aside from an unsightly appearance and the early defoliating of the tree and affecting its shade benefits and beauty is rarely serious to established trees.
Established trees may be affected by Anthracnose during the budding out season if it is unusually wet and cool; especially for Maple trees. A purplish brown outbreak of circular spots will occur along the vein of leaves, possibly turning to darker brown. The beautiful Maple may lose its leaves early, but a singular episode is not cause for alarm. Yearly outbreaks would be more serious and could weaken the tree significantly for other diseases to affect them also, like borers and winter frosts.
Oak tree infections give the tree a scorched look and affect the lower branches. Any acorn fruit would have a small watery sunken circle on it, that may or may not produce a gelatinous pink spore mass. Never prune Oak trees in April, May or June, as this lays the foundation for beetles that may spread Anthracnose and/or other diseases.
For both Maples and Oaks, usually just cleaning up the fallen diseased leaves and destroying them, and pruning diseased branches and attending the tree with water, fertilizer and mulch will bring the tree back to good health. Fungicides are rarely needed, but can be used in more severe outbreaks.
Other signs of Anthracnose may but not necessarily be present such as small black spots, cankers at the stems of leaves or the stalk, called a petiole, and rotting leaves and roots. After defoliation, if the growing season is early enough, a tree may rebound and produce new leaves. This disease for shade trees is a common threat and watched for by arborists and tree experts wherever shade trees thrive.