Delaying the Onset of Fungicide Programs for Control of Apple Scab in Orchards with Low Potential Ascospore Dose ofVenturia inaequalis

Conventional fungicide spray programs for the control of apple scab have long involved the application of fungicides prior to the pink stage of fruit-bud development. Our earlier studies, which showed a relationship between the relatively low levels of overwintering inoculum found in modern commercial orchards and the onset of scab epidemics, indicate that early-season fungicide sprays are not necessary in many commercial orchards in the northeastern United States. To test this hypothesis, experimental plots were established in several commercial orchards in New Hampshire and New York, and tests were run from 1985 to 1991 (.)