Plant Health Care Tips: Anthracnose
Strange, irregularly shaped brown splotches clearly don’t belong on shiny, green tree leaves. Anthracnose is a disease that commonly causes these unsightly spots.
On each type of tree, anthracnose looks a bit different. On ash trees, anthracnose appears as irregularly shaped brown areas on new leaves with additional brown blotches on leaf tips and veins. On maples, brown lesions form along leaf veins. On oaks, anthracnose creates large, dead areas between leaf veins.On sycamores, leaf veins and adjacent tissue slowly turn tan and then brown. On all tree varieties, prolonged periods of cool, wet weather after bud break usually cause the disease to strike and then spread.
Protection from Infection
Fertilizing anthracnose-infected trees and watering during dry periods typically help the tree overcome stress caused by the disease. As infected leaves fall, rake them up and dispose of them to avoid exposing other trees. Pruning infected branches can also limit the spread of the disease.
As leaves emerge in spring, arborists may recommend foliar fungicide applications to minimize infection and defoliation. On sycamores, a professional trunk injection of fungicide can provide up to two years of disease suppression.