Chemical control is usually not necessary but fungicides can be applied as soon as symptoms are detected. Among the compounds registered for use in Connecticut are potassium bicarbonate, benomyl, thiophanate-methyl, horticultural oil, chlorothalonil, and triadimefon. Consult the label for dosage rates and safety precautions. Gray mold, Botrytis cinerea. In prolonged rainy seasons flowers and some shoots may be blighted with the gray mold fungus.
Flowers appear to fade very suddenly, and leaves shrivel.
The gray mold fruiting stage is usually found on affected parts. A change in weather will clear up the trouble. Blighting of new shoots is black in color, starting as spots on leaves and branches which rapidly involve the entire shoot. Bacteria may be found in abundance in diseased tissues, including the wood. Many newer varieties are resistant to infection.