Ash tree leaves dropping

Asked June 6, 2014, 8:43 AM EDT

Three large ash trees in our yard are dropping leaves. One tree looks like all it's leaves have turned brown and are dropping. Are these trees dying?

New Castle County Delaware

1 Response


Thank you for contacting Delaware Cooperative Extension. What you describe and show in your picture is a disease called ash rust, caused by a fungus. It causes leaf spots and distortion to petioles and twigs and the fungus only affects ash trees, so it will not infect other trees and shrubs on your property. It is too late for control now. We see ash rust each year, but some years it is more prevalent. The alternate host of the ash rust fungus is Spartina marsh grass, so the spores go to grasses from the ash trees. The incidence of ash rust is always dependent on the weather and wind conditions in the spring when leaves are expanding and spores are produced on the marsh grass. Trees can tolerate some rust infection, and new leaves will come out to replace ones that drop. Rake up and remove leaves that drop to remove spores that might infect marsh grass within a 10 mile range. Hopefully, next year will not be favorable for this plant disease.

My best,