On peaches, fruit are first susceptible starting 5-7 days after shuck split. Periods of rainfall with temperatures of 65-75 F are optimal conditions for infection. Although fruit remains susceptible until harvest, the 4-week period following start of shuck split is the most critical period for infection to occur. The time from infection until lesions are visible may be 4-6 weeks. Thus, infections occuring within 4 weeks of harvest do not result in visible lesions.
All varieties are susceptible to scab, with some being more severely effected than others.
This results from the large numbers of twig lesions that develop during the first two growing seasons. Low-lying planting sites should be avoided and trees should be properly pruned to allow good air circulation, thus promoting rapid drying of fruit, twigs and leaves. Fungicides such as captan and wettable sulfur provide adequate control of this disease if applications are properly timed. On peaches, sprays should begin about 1 week after petal-fall. Sprays on nectarines and apricots should begin at about petal-fall.