This foliar disease was confirmed on Long Island for the first time during August 2021 in a high tunnel cucumber crop. Favorable conditions for disease development are leaf wetness when hot (79 – 90 F), thus it mostly occurs in tropical and subtropical regions.
Leaf spots are generally round, small, and develop on lower leaves first. They were light tan on the cucumber. The disease is also reported common on melons and can occur on other cucurbits. Spots are brown on watermelon. Symptoms can also develop on petioles and stems. The pathogen produces long gray conidiophores resembling short, straight eyelashes which were visible using a dissecting microscope, especially on leaves incubated inside a plastic bag.
Management practices include applying fungicides, destroying crop debris after harvest (physically removing from high tunnel is worthwhile), and rotating where cucurbits are grown. Chlorothalonil is labeled for this disease, but not permitted used in greenhouses. Fungicides such as copper and Double Nickel that are labeled for diseases caused by Cercospora in other crops may provide control when applied for other diseases in cucurbits.
Please Note: Fungicides mentioned are for use in commercial production, not gardens. The specific directions on pesticide labels must be adhered to — they supersede these recommendations if there is a conflict. Any reference to commercial products, trade or brand names, is for information only; no endorsement is intended. For up-to-date information on labeled conventional fungicides see Cornell Integrated Crop and Pest Management Guidelines for Commercial Vegetable Production and biopesticides see the Biopesticides website.
Following 3 photographs were taken in a high tunnel by Sandra Menasha, Vegetable/Potato Specialist with Cornell Cooperative Extension-Suffolk County.
