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Extension > Garden > Yard and Garden > Vegetables > Diseases of cucurbits > Angular leaf spot

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Angular leaf spot

Michelle Grabowski

Leaf with white spots

M.Grabowski, UMN Extension

Angular leaf spot is a bacterial disease caused by Pseudomonas syringae pv. lachrymans. Although angular leaf spot can occur on any of the cucurbit crops, cucumber is less commonly affected due to the availability of resistant varieties.


Important biology

Close up of leaf with yellow spots

M.Grabowski, UMN Extension

Angular leaf spot thrives in warm humid conditions. The bacteria can infect all cucurbit crops and will infect all above ground parts of the plant including leaves, fruit and vines. When fruit are infected, the bacteria moves deep into the fruit and infects the seed.

The disease can be introduced into a field through contaminated seed. When humidity is high, a drop of clear to white sticky bacterial ooze forms on infections. These bacteria are moved from plant to plant on the hands and tools of workers, by insects, or by splashing water. The pathogen can survive in plant debris for over 2 years.


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