Varieties differ in susceptibility so use of resistant varieties can be effective to reduce infection. Fungicide sprays are also very helpful to control this disease and applications can be made as soon as new growth emerges in the spring. Among the compounds registered for use in Connecticut are chlorothalonil, mancozeb, triadimefon, and sulfur. Consult the label for dosage rates and safety precautions. Leaf spots, Cercosporella, Ascochyta, Alternaria .
Symptoms develop on leaves and can be circular to angular in appearance.
These spots are typically scattered over the leaf surface although the size, color, and margins of the spots vary with the specific fungus. When infections are heavy and the spots coalesce, leaves appear tattered. Efforts to maximize plant vigor by fertilizing and watering are helpful. However, watering should be done early in the day to give the foliage a chance to dry before nighttime. It is also helpful to pick and remove symptomatic leaves as soon as they develop.