A: Most likely a fungus is causing the leaf spot on your azalea leaves. Be sure the irrigation heads are not hitting the leaves directly; it would be better for the plant to receive water at the root area. The water splashes on the leaves and spreads the fungal spores from one part of the leaf to another part. The fungal spore enters into small openings on leaf and cause the damage and spots. Any new leaves produced may be sprayed with fungicide so be sure to have the chemical ready in the spring and summer when the fungus is peaking. Use any fungicide labeled for use on ornamentals. A common fungicide used on roses would be a possibility. Please read the label thoroughly and follow the instructions. The older, spotted leaves will not be changed by applying fungicide so do not waste it on them. You might consider some light pruning but do not over do it. If you prune now, you will lose some of the flowers expected in the spring so remember “lightly” is the operative word. Attached is a publication on azaleas which contains common diseases and pests. http://edis.ifas.ufl.edu/MG019
Q: What might be causing the spots on my azalea leaves?