If leaf spots are seen, pick off and destroy the infected leaves or use sprays containing basic copper sulfate.
If bacterial leaf spot causes problems, pick off and destroy infected leaves. No chemical control is listed.
Canker can kill branches or entire plants. Bright, reddish-orange fruiting bodies may appear on the bark. No chemical control is available. Prune out infected branches.
Flowers may be infected with blight caused by Botrytis cinerea. Use sprays of benomyl.
Bud drop can be caused by too much or too little water or over fertilization.