Angular leaf spot is a bacterial disease which can affect cucumber and many related species. Leaves initially develop small, water-soaked spots which enlarge until limited by the larger veins. The lesions are typically angular in shape rather than round. The spot may exude clear or milky droplets of bacterial ooze on the underside of the leaf. The droplets dry to a whitish, crusty layer. Leaf lesions often turn tan and tear away from the leaf, leaving ragged, irregular holes. Spots also appear on stems, vines, and fruit. Lesions on fruits are typically small, circular, water-soaked spots. These spots may be associated with an internal fruit rot. The bacteria are spread by splashing water, insects, and mechanical means including hands and tools.

Management Options

Non-Chemical Management

Plant disease-free seed.
Rotate crops. Do not plant cucumber or related crops in the same location for at least two years.
Plant resistant varieties. Resistant varieties may still become infected, but will suffer less damage. Pickling varieties: 'Calypso, 'Cross Country', 'Express', 'Frontier', 'Pioneer', 'Regal', 'Royal'. Slicing varieties: 'Bel Aire', 'Dasher II', 'Encore'
Avoid overhead watering.
Wash with soap and water after handling plants. Do not handle healthy plants after working with infected plants. Do not handle wet plants.

Select non-chemical management options as your first choice!

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides

Applying fixed copper products have reduced disease spread, but may cause stunting and leaf chlorosis. NOTE: Lilly Miller Kop-R-Spray Concentrate is labeled ONLY for cucumber and squash.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

Bonide Copper Fungicide Spray or Dust RTU [Organic]
Active ingredient: basic copper sulfate | EPA reg no: 4-58
Bonide Liquid Copper Fungicide Conc/Organic Gardening
Active ingredient: copper octanoate | EPA reg no: 67702-2-4
Soap-Shield Flowable Liquid Copper Fungicide [Organic]
Active ingredient: copper octanoate | EPA reg no: 67702-2-56872
This list may not include all products registered for this use.

Images

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Caption: Angular leaf spot on cucumber Photo by: R.S. Byther
Caption: Angular leaf spot on cucumber Photo by: R.S. Byther
Caption: Bacterial infection on zucchini Photo by: R.S. Byther

WSU Extension

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