These diseases can be minimized by cleaning up plant refuse in the fall and by adequate spacing of the plants to promote good air circulation. Although not usually necessary, applications of fungicides can be made when new growth emerges in the spring. Among the compounds registered for use in Connecticut are mancozeb, maneb, and triadimefon. Consult the label for dosage rates and safety precautions. Botrytis blight, Botrytis cinerea.
Flowers turn a papery brown and become covered with gray, fuzzy masses.
Senescing flowers are particularly susceptible. Tan to brown spots with a target-like appearance can also develop on the leaves. These patches are often associated with flowers which have dropped onto the leaf surface. This disease is particularly troublesome during periods of extended cloudy, humid, wet weather. Good sanitation practices including grooming the plants and removing spent or senescing flowers can minimize the potential for infection.