Angular leaf spot is a bacterial disease affecting cucumber and other cucurbits, including squash, pumpkin, and melon. The infection begins with small, angular, brown to straw-colored water soaked spots on the leaves, usually confined within the veins of the leaves and often with yellow halos. As the disease progresses, the leaf spots dry, and the center of the spot falls out leaving an irregular hole. Petioles, stems, and fruits may also be affected. When lesions develop on the fruit, the bacteria may also infect the seed. In addition, the lesions provide an entry way for soft rot bacteria that may entirely rot the fruit. A sticky white exude may form on the underside of the leaves and become crusty when dry. Warm, humid, rainy conditions, and high soil nitrogen favor the development of the disease which is spread by infected seed and plant debris, water, workers, and machinery that has had contact with diseased plants. Photo Credit Clemson, Wikipedia
Control
- Choose resistant varieties (many are available).
- Use only disease-free seed and rid the garden of volunteers in previously infected areas.
- Practice a three year crop rotation with plants from other families.
- Water in the morning and use drip irrigation or hand water close to the soil.
- Work with the plants only when plants are dry.
- Remove diseased plant material promptly.
- Remove all plant debris at the end of the growing season.
- Apply fertilizer containing nitrogen with caution.
- In severe cases use copper combined with mancozeb early in the season at the appearance of the first symptoms.
Karen Meyers