Our mountain ash tree has white spots on it and the leaves are falling off. Can you help?
The condition you describe is most likely powdery mildew, which is caused by fungus. A wet winter provides ideal conditions for the development of the disease. It can also be caused or promoted by a lack of sun on the plant or insufficient circulation (air) through the crown. Check with your local nursery for natural treatments to suppress the disease and/or have the tree pruned to open up the canopy for better air circulation. You can also prune back other plants to give the ash more light.
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