Hello, We recently ( a month ago) planted an American Mountain Ash. Right after planting it we noticed that the leaves on some branches are not healthy and they look like dying but they are green. This problem is spreading through the tree now and other branches are also affected. We have watered it regularly, and we mixed fertilizer with soil when planting it. Today I noticed that there are discoloration on the leaves. I took a picture and you can find it attached to this conversation. Does anyone know what the problem could be? I loves ash trees and I really hope that it is not dying :(
Your tree appears to be infected with Powdery Mildew, to which it is known to be susceptible. The brown discoloration looks more like leaf scorching from excessive fertilizer in the soil. Did you use slow-release or standard chemical fertilizer?
Hello Vitog, Thank you very much for the response. We used CIL 18-4-6 fertilizer and it is a slow release. If it is excessive of fertilizer then is there anything we can do about it? What causes the powdery mildew? any treatments? does it kill the tree? I really appreciate your help.
Slow release fertilizer should not cause leaf scorching; however any excessive salt in the soil can have that effect. It's not planted near a road, is it? The only treatment for excessive salt that I'm aware of is leaching it out of the soil by watering a lot. Powdery Mildew is a fungus disease that proliferates during warm, damp weather. My tomatoes were affected this year during a warm and rain-free but fairly humid summer. I used copper spray to minimize the damage, but I don't know if copper is effective for Mountain Ash. You could try sulphur spray, which is used for mildew on grapes. The garden centre or nursery where you bought the tree might be able to give you some advice on treatment. Another option is to try one of the many treatments shown on the Web for Powdery Mildew on roses, since Mountain Ash is a member of the rose family.
