Refining and Validating a Fungicide Timing Model for Controlling Flyspeck on Apples in the Hudson Valley

Abstract

Flyspeck is caused by the fungus Zygophiala jamaicensis and appears during the late summer as superficial blemished on apple fruit. Development of flyspeck is favored by the hot and humid summer climate in the Hudson Valley, but this disease causes commercial losses throughout the Northeast in wet years. Inoculum for flyspeck infections on apples probably originates with host plants outside of the orchard. More than 100 plant species are hosts for this fungus. Researchers in Massachusetts have reported that disease incidence in unsprayed orchards was significantly higher in trees located within 90 meters of external inoculum sources. Disease incidence is also greater in orchards with poor air drainage because trees dry more slowly following rains and dews.