My cucumber, cantaloupe, squash, and pumpkin leaves have a white powdery substance on them and are dying. What is the problem?
Cucurbit leaves infected with powdery mildew initially show symptoms of mottling and yellowing. Signs of the causal fungi, Erisyphe cichoracearum or Podosphaera xanthii, appear as a whitish, talcum-like, powdery growth on upper or lower leaf surfaces. The affected leaves can wither and die and, finally, become dry and brittle.
Fungicides for powdery mildew management are available for home garden use. Apply at the first sign of disease and then at weekly intervals. Be careful to read the label about the days-to-harvest restrictions for these fungicides. Contact your local Extension office for fungicide recommendations.