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Table: Diagnosis and Control of Ash Anthracnose
Pest Identification Host Plants Damage Symptoms
Ash Anthracnose
Apiognomonia errabunda
Ash trees Leaves and shoots of infected trees may appear blackened and deformed, or spotted. Older more mature tissue is more resistant and may only appear spotted (brown necrotic spots), while younger tissue is more susceptible and may appear brown or blackened and deformed. Anthracnose may cause partial or complete defoliation of trees. However, trees that defoliate early in the season will usually send out a second flush of leaves. This disease usually infects the lower portion of the canopy first and then progresses upward.
Monitoring Control Options Pesticides
Watch for brown necrotic spots to develop on leaves in the lower canopy. Infections should begin in early spring during periods of cool wet weather. As the season progresses disease should become less active. Anthracnose is usually considered a cosmetic disease that does not require chemical control. In severe cases where anthracnose has defoliated the tree for 3 out of 5 years, chemical control may be warranted. A fungicide spray using thiophanate-methyl at the time of bud break and again 7 to 10 days later should effectively control this disease. Additional sprays may be applied during cool wet weather according to the label. More than one year of control may be needed. Additional control measures include pruning infected branches and cultural practices to increase the vigor of the tree. Sanitation and eradication appear to be of little value, due to the overwintering of spores in the tree. Thiophanate-methyl,
(Clearys 3336)
Description and Life History
Description: Anthracnose is a fungal, foliar disease that infects the leaf tissue, and shoots. Anthracnose can cause blight of leaves and shoots, as well as twig dieback. Spores are produced in acervuli on infested tissue.

Life history: Anthracnose is activated in the spring by cool wet weather. Spores produced on mycelium overwintering in infected twigs or leaves penetrate the lower surface of the leaf and continue to progress into the petiole and twig. The fungus then produces spores during wet periods.

Overwintering: Anthracnose overwinters in infected twigs or on dead debris.


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Last modified on March 06, 2013