Issue with Mountain Ash Tree
Hello: I work at the Cottonwood County Extension office in Windom, MN. I had a gentleman come into my office with questions regarding his Mountain Ash tree. The leaves are falling off and have brown and yellow spots on them. I have taken two photos of the sample - a front and back of the leaf. Can you please tell me what his issue is and how he should proceed to fix it. Thank you. Teresa Schwartz - firstname.lastname@example.org or 507-831-4022
Thank you for your response Bob. A follow up question to this, if I am reading the bulletin correct, at this point in the summer there is really no spray that can be used to fix the problem for this year. Should my homeowner be applying something next Spring? Second question, does this come back from year to year if left untreated? Thank you.
Jumping in on this because I am curious about this tree. I have never seen a mountain ash with leaves like this; they are typically compound leaves with many small leaflets. The leaves in this sample appear to have only 2 small leaflets and then a large, terminal leaflet shaped like an oak leaf. I do not believe this is a mountain ash, and if not, the diagnostics and recommendations might be very different.