Angular leaf spot

   The bacteria Pseudomonas syringae pv. lachrymans, occurs on most cucurbits but is more prevalent in cucumbers. Outbreaks are likely under continuous rainfall and 75-80F. First symptoms are small, water-soaked angular lesions on the leaf underside. Lesions, restricted between the small cucumber leaf veins, turn yellow, develop yellow hollows, and finally disintegrate. Under wet conditions, such as early in the morning bacteria oozes from the lesions which later dries into a white crust. Expanding leaves which are close to full size are most susceptible to infection. Old leaves tend to be resistant. Young leaves can be infected mechanically by insects or field workers. Infected stems, petioles and fruits also develop water soaked lesions. Fruit lesions are more circular, turn white, and crack open. This openings allow for secondary infection by other organisms. The bacteria survives on infected plant refuse and on seed. The disease is spread by wind, rain, insects, and field workers. Damaged plants with wounds from wind or sand are especially susceptible to infection. Controls include a 2-3 year rotation, use of disease-free seed, and weekly sprays of a broad-spectrum fungicide such as chlorothalonil plus a copper fungicide. Be aware that high copper application rates may result in crop injury, especially during the early crop stages. Resistance or tolerance is available in Centurion, Dasher II, Early Triumph, Floracuke, Raider, Spring 440, Pointsett 76-S and other commercial cultivars.