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Anthracnose in cucurbit crops

Anthracnose occurs occasionally in cucurbit crops in the Northeast.  Following pictures of cucumber leaves taken on 7 and 15 August in 2014 show how symptoms can change in appearance in just one week.  The circular leaf spots are initially water-soaked, then become yellow to tan.  Round, black, sunken spots can develop on fruit.  On fruit spots the pathogen produces diagnostic salmon-colored spores under moist conditions.



This disease rarely reaches damaging levels resulting in impact on yield or fruit quality, with the exception of winter squash as anthracnose can be a postharvest problem.  Melons (all types) are considered moderately susceptible while other cucurbit crops have low susceptibility.  Warm, moist conditions are favorable.  The pathogen can be seed-borne and survives in crop debris.

Manage anthracnose by growing resistant cucumber varieties, selecting pathogen-free seed, applying fungicides, destroying crop debris as soon as possible after harvest, and rotating out of cucurbit crops for at least two years.  Contact (protectant) fungicides containing chlorothalonil, mancozeb, and/or copper are labeled for anthracnose. Fungicides with targeted activity include Cabrio, Quadris, Inspire Super, Pristine, Tanos, and Topsin M.

 Please Note: 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.

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