Powdery Mildew
(fungus - Erysiphe cichoracearum and Sphaerotheca fuliginea): 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, stunted, and may die. Fruits are
not attacked, but are usually small and deformed. Powdery mildew is favored by
cool, dry weather. Spores are air-borne. For most cucurbits there are resistant
varieties. Preventative fungicide applications will effectively
control powdery mildew. New races of the fungus have appeared which are resistant
to some fungicides. Several applications may be necessary for optimum control.
