Angular Leaf Spot of Cucurbit Crops
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Angular leaf spot (Pseudomonas syringae pv. lachrymans) primarily affects cucumber but may occur on muskmelon, squash, pumpkin, and watermelon. Leaves develop small, water-soaked spots (lesions) that later enlarge. The shape of older lesions tend to be angular as they enlarge and encounter veins. Under very humid conditions and warm temperatures, white ooze may be found on the underside of lesions. Stems and fruit may develop water-soaked spots and necrosis.
Angular leaf spot on cucumber foliage.
(Photo: USDA Cooperative Extension Slide Series, Clemson University, Bugwood.org)
Management:
- Pathogen-free seed
- Hot water treatment of seed (cucumber only)
- Crop rotation
- Irrigation management (minimize leaf wetness and soil splash)
- Proper ventilation (greenhouses)
- Resistant varieties
- Applications of fixed copper
