Windblown spores are deposited on expanding leaves where they germinate and penetrate the leaf surface. Germination and infection of the host requires that the leaf surface remain wet for a period of time, the length of which varies according to the ambient temperature. The best means of avoiding scab is to plant resistant cultivars. Several cultivars of flowering crab are available with good resistance to scab, fireblight, and cedar-apple rust. Disease resistance, aesthetic quality, and adaptability to Kansas conditions should all be considered before choosing a flowering crab for planting.
Most apple cultivars are moderately to highly susceptible to scab.
Recently, several new apple cultivars have been released with excellent resistance to scab and some other diseases, and should be considered before planting to reduce the number of pesticide applications. Since the fungus overwinters on fallen leaves, the disease may partially be controlled by raking and burning or removing leaf debris in the fall. This will not give complete control, since even a few leaves missed during sanitation can start the infection process in the spring. For susceptible flowering crabs, several fungicide applications may be required for control. The most critical spray period is in the spring when primary spores are being released from leaf debris.