Integrated approaches for management of Phytophthora blight (Phytophthora capsici) of cucurbits

Phytophthora blight, caused by Phytophthora capsici, is the most important disease of cucurbits in Illinois and many of cucurbit growing areas in the world. There is no cucurbit cultivar with measurable resistance against Phytophthora blight available. At present, cultural practices and chemical use are the options for management of this disease in cucurbit fields. A research program was established to develop effective strategies for managing Phytophthora blight of cucurbits by integrating cropping rotations, seed treatment, field scouting, using short-cycle mustard as cover crop, and fungicide sprays. Cropping rotations of ≥3 years with nonhost crops was established after the host range and survival of P. c a p s ic i in soil were determined. Seed treatment with mefenoxam (Apron XL LS at 0.42 ml·kg ^-1 of seed) and spray applications of captan (Maestro 80DF at 6.73 kg·ha^-1), copper (Kocide-3000 46.1DF at 2.24 kg·ha ^-1), cyazofamid (Ranman 400SC at 0.20 L·ha^-1), dimethomorph (Acrobat 50WP at 0.46 kg·ha^-1 or Forum 4.16SC at 0.44 L·ha^-1), famoxadone-cymoxanil (Tanos 50DWG at 0.70 kg·ha^-1), folpan (Folapn 80WDG at 6.73 kg·ha ^-1), mandipropamid (Revus 2.09SC at 0.58 L·ha^-1), mefenoxam (Ridomil Gold Copper 65WP at 2.24 kg·ha-1), phosphorous acid (ProPhyt 4.2F at 2.84 L·ha^-1), reduced yield losses from more than 30% to less than 10% in cucurbit fields. Field scouting and removing/disking infected plants in small areas in the early disease development stages helped to delay the spread of the disease in the fields. Amending soil with mustard reduced the incidence of vine and fruit infection of pumpkin caused by P. capsici.