Downy Mildew
(fungus - Pseudoperonospora cubensis): Angular yellow spots appear on the
upper surface of the leaf during periods of high humidity. The underside of leaves,
opposite the yellow spots, becomes covered with grayish growth which is the spore
producing structures of the fungus. This growth is more noticeable early in the
morning when heavy dew is present. Spores are easily carried by wind from diseased
plants. Cool temperatures along with free moisture are ideal for mildew infection
and spread. Hot, dry weather may reduce or stop disease development. Resistant
varieties should be used when possible. Preventative fungicide
applications should begin at bloom and continue until the crop is harvested.
