2018 ASHS Annual Conference

Phytophthora blight, caused by the oomycete Phytophthora capsici, is one of the most important diseases of cucurbits worldwide, causing up to 100% crop losses. Major symptoms caused by P. capsici on cucurbits are seedling death, foliar blight, and fruit rot. P. capsici also infects more than 40 species in 15 plant families. There is no cucurbit cultivar with measurable resistance against Phytophthora blight available. Cultural practices and chemical use are the options for management of this disease in cucurbit fields. We developed effective strategies for managing Phytophthora blight of cucurbits by integrating cropping rotations, seed treatment, field scouting, and fungicide sprays. Cropping rotations of ³ 3 years with nonhost crops was established after the host range and survival of P. capsici in soil were determined. Seed treatment with mefenoxam (0.42 ml Apron XL LS/kg of seed) and spray applications of effective fungicides reduced yield losses from up to 100% to less than 10% in commercial fields. In the past 15 years, more than 10 new fungicides with different modes of action were registered for management of Phytophthora blight of cucurbits. Field scouting and removing/disking infected plants in small areas in the early disease development stage helped to delay the spread of the disease in the fields. Plant should not be irrigated from pounds that contain water drained from infested fields.