Cucurbit Downy Mildew

What Is It? | Facts in Depth | For the Professional Diagnostician

Anna L. Testen and Sally A. Miller

Cucurbit downy mildew is an important foliar disease that affects all types of cucurbits.  This disease is caused by the fungus-like pathogen Pseudoperonospora cubensis.  Cucurbit downy mildew spreads rapidly and can cause extensive yield loss.  Management of cucurbit downy mildew relies on cultural practices to reduce moisture on leaves and fungicide applications based on a disease forecasting and monitoring system.

 Scientific Name

  • Pseudoperonospora cubensis

Host Crops

  • Cucumber
  • Melon
  • Squash
  • Pumpkin
  • Watermelon

Cuc DM-5compressed 50 QUALITY Cucumber DM-6 50 QUALITY Cucumber DM sporulating2 50 QUALITY Cucumber DM Huron cnty1 50 QUALITY Cucumber DM Huron cnty2 50 QUALITY
Pictures of lesions caused by downy mildew on the top (top left) and underside (top middle) of cucumber leaves; sporulation of the pathogen (top right); and infected cucumber fields (bottom row).