Powdery Mildew in Cucurbits

With the arrival of cooler nights and heavy night dews, conditions are right for powdery mildew to thrive.  As a matter of fact this year it has been seen on a number of crops earlier than usual due to wet weather.  The disease appears on leaves as a white powdery mass composed of the spore-bearing structures of the fungus.  The disease can affect entire fields.  Severely infected leaves shrivel and die. The fungus can also grow on petioles and young stems.  Infected plants are yellow and stunted. Pictures of powdery mildew in cucurbits can be found here .

Fruits are not attacked, but are usually small and deformed.  The spores are air-borne.  Resistant cultivars exist.  Preventative fungicide applications will effectively control powdery mildew.  For more information on fungicides registered for control of powdery mildew in cucurbits see the Pumpkin & Squash Management Schedule – a guide to insect, weed and disease management.