Anthracnose refers to fungal plant diseases that cause irregular dead areas along leaf margins and across and between veins. Entire leaves, young shoots, and twigs may be killed. Anthracnose diseases usually occur during cool, wet spring weather and may continue through early summer if rainfall is above normal. Chemical control of these diseases is rarely recommended, as anthracnose diseases rarely lead to death of mature shade trees. Applying fungicides after symptoms appear usually does little to help the tree, as most of the damage has already occurred. Fungicides may be applied at bud break when young leaves begin to unfold and must be applied biweekly as long as conditions favor disease development. Contact your local Cooperative Extension office for fungicide recommendations. Fungicide application for most trees is impractical and not necessary.
Ash anthracnose occurs during cool, wet weather. This disease may cause premature leaf drop. Chemical control measures are not recommended, as mature trees are rarely harmed by this disease. Raking and composting diseased leaves may reduce disease incidence next season.
Maple anthracnose is most common when spring weather is unseasonably wet. Red and sugar maples are often hosts of this disease. While leaves may be distorted and canopies thinned, damage is rarely permanent. Raking and composting diseased leaves may reduce disease incidence next season.
Oak anthracnose may cause leaf spots that merge to form large blighted areas. Mature trees are rarely seriously harmed by this disease. Rake and compost diseased leaves.
Sycamore anthracnose is one of the most damaging diseases in this group. Not only are leaves infected, but succulent twigs and small branches may be killed. Repeated infection may slow growth. Chemical control is rarely recommended, as preventative sprays are most effective but impractical for most gardeners to apply. As with other anthracnose diseases, incidence may be reduced by raking and composting diseased leaves. Fertilization may increase the vigor of affected trees. Platanus x acertifolia (London Planetree) cultivars resistant to anthracnose include 'Bloodgood,' 'Columbia,' and 'Liberty.'
Spot anthracnose refers to a disease of dogwood in which small, red lesions form on flower bracts and leaves. Flower bracts may be off-color, distorted, and smaller than normal. Leaves may be distorted if leaf spots form during leaf expansion. Chemical control is only recommended for valuable specimen trees that have a history of this disease. Contact your local Cooperative Extension office for fungicide recommendations. Resistant cultivars of flowering dogwood include 'Plena,' 'Cherokee Princess,' 'First Lady,' 'Spring Time,' and 'Fragrant Cloud.'
Dogwood anthracnose caused by the fungus Discula destructiva was first observed in the late 1980s in the southern Appalachians. It can cause significant damage to native flowering dogwood growing as an understory tree in forests and landscapes. This disease can cause serious blighting of foliage and large cankers on the trunk of infected trees, which lead to death if the trunk is girdled. Small trees can be protected with fungicide sprays during cool, wet periods in late spring and early summer. Contact your local Cooperative Extension office for fungicide recommendations. Also, Cornus florida 'Appalachian Spring' is an anthracnose-resistant dogwood that can be planted in areas where dogwood anthracnose is problematic.
