Anthracnose on Shade Trees Insects & Diseases
Host Plants • Ash – Fraxinus • Oak – Quercus • Sycamore – Platanus • Maple – Acer • Dogwood – Cornus • Grapes - Vitis • And others….
Causal Organism • Anthracnose is caused by various species of fungi in the genus Apiognomonia. • Each species is specific to the host tree it infects.
Symptoms • Small dead spots on leaves. • Dead leaf margins and tips. • Brown, dead leaf areas along the leaf veins. • Premature defoliation. • Twig death. • Formation of a witches broom. Sycamore Sycamore Sycamore
Sycamore Ash Sycamore Sycamore
Disease Cycle • The fungus survives the winter on stem cankers fallen leaves. • In the spring the wind carries the spores from the cankers to developing leaves and twigs. • Young, infected twigs are girdled and killed. • New spores forming on infected leaves and twigs are blown or splashed to nearby foliage. Infected leaves shrivel and fall. • Cool, wet spring weather (50-55 degrees F.) favors the spread of this disease.
Management • Remove fallen leaves. • Prune out diseased twigs and branches. • Open up the canopy for better air circulation and light penetration. • Spray a fungicide labeled for anthracnose beginning at bud break and continuing weekly until the weather warms into the 60’s.
References • Penn State University Plant Disease facts • Iowa State University Plant and Insect Diagnostic Clinic • Cornell University Fact Sheet