- Worldwide distribution. On members of the cucumber family (cucurbits): important on cucumber, rockmelon and zucchini, but also on gourd, melon, pumpkin, squash, watermelon, zucchini.
- Not a fungus, a water mould, or oomycete. Spots yellow, then brown, merge; leaves dry and die.
- Spread is by wind and water splash, and long distance in air currents when humidity is high. Survival is on volunteer plants and weeds.
- Cultural control: avoid overhead irrigation; space plants to allow air movement; avoid planting in warm and wet times of the year; tolerant varieties available (melon, cucumber, watermelon); weed.
- Chemical control: copper, chlorothalonil, mancozeb (protectants); metalaxyl, phosphorus acid (systemics).
