Collect and remove fallen leaves. Usually, disease is not serious enough for fungicidal control, except in unusually wet seasons or locations with severely restricted air circulation.
Green ash is relatively resistant.
Trees lose large branches over several years and may die. No one cause has been identified. It is probably a complex of insect, disease and environmental problems, such as moisture stress and freeze injury. A close association between ash decline and ash yellows, caused by a phytoplasma, has been reported. Follow standard horticultural practices for pruning, fertilizing and watering.