Phytophthora Blight

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

Anna L. Testen & Sally A. Miller

Phytophthora blight of cucurbits, caused by the fungus-like pathogen Phytophthora capsici, is an increasingly important disease of cucurbits.  This disease affects all parts of cucurbit plants and can rapidly destroy fields of mature plants and cause postharvest fruit losses.  This pathogen spreads rapidly in wet, waterlogged soils, so site selection and water management are critical for managing this disease.

Scientific Name

  • Phytophthora capsici

Host Crops

  • Cucumber
  • Melon
  • Squash
  • Pumpkin
  • Watermelon

CukePhytoph1 50 Quality Phytoph pumpkin 50 Quality Phytoph winter squash 50 Quality PhytophPumpkinLeaves4 50 Quality PhytophPumpkinLeaves1 50 Quality Phytophthora sporangia 50 Quality
Phytophthora blight symptoms on cucumber (top left); pumpkin (top middle); winter squash (top right); and pumpkin leaves (bottom left and middle); and sporangia from the pathogen under a microscope (bottom right).