Leaves 'eaten' on Mountain Ash

Asked June 21, 2016, 10:33 AM EDT

Greetings. Ten-year old mountain ash shows signs of stress. About one-quarter of the branches are denuded; almost looks like the leaves were eaten. I find no insects on the tree. Doesn't seem like fire blight. Any other possible affliction that can be treated?

Rice County Minnesota

3 Responses

Could you tell me if the remaining leaves are healthy? Are they the same size and color on the entire tree? Brown or discolored? Do the branches or trunk have any unusual cracks, spots or discoloring? How close is the tree to a sidewalk or road? Thank you for any further information you can provide to help in getting you information.

Thanks, Amy J. There are no unusual cracks, spots or discoloration on the trunk or the branches. The tree is in a backyard garden so is not close at all to sidewalk or road. At this point--and the problem spreads daily--about 30% of the tree branches are affected. Leaves do not brown or discolor; they disappear, apparently by being consumed. Still, I can find no parasite on the leaves or branches. Very strange. Thank you.

It does sound as though something is consuming the leaves. There are some leaf eating caterpillars that defoliate ash. Typically you would see webbing or evidence of the larva. I would recommend you have an arborist from a local tree care company come and take a look.