This disease has been seen regularly on Long Island and also in western New York primarily on sugar snap peas. Source of the pathogen is alternate hosts including weeds (Pisum, Medicago, Vicia, Lupinus, and Lens spp.) and the pathogen can be seed-borne. Favorable conditions are warm, dry days with nights that are cool and dew forms. Frequent rain is not favorable.
There are resistant varieties. In a garden where powdery mildew occurred regularly and often severe on sugar snap peas, no powdery mildew was found on Giant Oregon snow peas. Overhead irrigation has been recommended for managing powdery mildew.
Note: Some information above from the Compendium of Pea Diseases.
Following photographs taken 5 July 2017 are snap peas that became very severely affected, with powdery mildew developing on pods and causing black discoloration. Spring conditions were cooler and wetter than typical for the area.
