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Angular leaf spot (Pseudomonas syringae pv. lachrymans) primarily affects cucumber but may occur on any cucurbit. Leaves develop small, water-soaked spots (lesions) with yellow halos. Lesions become tan to straw-colored, enlarge, and become angular as they 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:

• Select resistant cultivars (cucumber)
• Use clean seed.
• Space plants for air circulation and rapid drying.
• Apply preventative copper or bactericide.
• Promptly remove and destroy diseased plant material during the growing season. 
• Manage weeds and potential alternative hosts.
• Avoid movement of infested soil to clean fields.
• Promptly destroy crop residues after harvest.
• Deep plow to bury residual inoculum.
• Rotate with nonhost crops for at least 2 years.

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