Early leaf drop on Autumn Purple Ash trees

Asked September 7, 2020, 1:26 PM EDT

I have two Autumn Purple ash trees that I planted over 11 years ago. For some reason this year lots of healthy green leaves started dropping in mid-August. One tree, the one in the photos, has had much more leaf drop than the other. During the first 2-3 years I deep watered the trees during the summer months but once established I stopped watering during the summer.

The photos show two shots of the most affected tree and one shot of what the leaves look like that are falling. This early leaf drop has never happened before and In every past Fall the leaves have turned color during September/October and fallen in October and early November.

I am trying to find out if this indicates a disease or problem with the trees. Any information would be appreciated.

Thank you

Multnomah County Oregon

1 Response

“Autumn Purple” ash trees suffer from several problems. The emerald ash borer, an invading pest, kills infested ash trees within five years if not sooner. Other insect pests include lilac borers, carpenter worms, leaf miners, ash sawflies and ash leaf curl aphids. Nests constructed out of webbing appear in ash trees infested with webworms. These are especially visible in the fall. Plant diseases like fungal leaf spots, powdery mildew, rust, anthracnose, and cankers can cause serious problems for the “Autumn Purple” ash tree.

Your tree is likely suffering from anthracnose. The disease is worse in wet years and is partially controlled by gathering and disposing of diseased, fallen leaves. Anthracnose is also called leaf scorch and leafspot. Infected parts of the leaves turn brown, along the margins. Infected leaves fall prematurely. Rake up and destroy infected leaves. Fungal diseases can be controlled in the early stage by pruning affected branches and fertilizing the soil with a low-nitrogen, high-phosphorous blend to ensure the tree has the nutrient it needs to fight the diseases off.

Hope this helps!