Phytophthora Blight of Vegetables

Phytophthora foliar blight and fruit rot, caused by Phytophthora capsici, has been observed in commercial fields and home gardens of cucumber, cantaloupe, pumpkin, squash, watermelon, zucchini, eggplant, bell pepper, and jalapeno throughout Illinois. Due to the frequent and heavy rainfalls, the disease is epidemic in some areas. To control Phytophthora foliar blight and fruit rot in cucurbit fields, the plants should be sprayed with Acrobat 50WP (dimethomorph) at the rate of 6.4 oz product (3.2 oz a.i.) per acre at the first sign of the disease. Continue applications on a 5-10 day spray schedule. Acrobat 50WP must be applied as a tank mix with another fungicide (e.i., copper, mancozeb). Cuprofix is an effective copper compound against Phytophthora blight. Do not make more than two sequential application of Acrobat 50WP before alternating to another effective fungicide with a mode of action different from Acrobat 50 WP (e.i., copper, mancozeb, Bravo) for at least one application. Do not make more than 5 application of Acrobat 50WP per season. Do not exceed 32 oz per acre per growing season. Do not use less than 20 gallons of water per acre for ground application and 5 gallons per acre for aerial applications. Cucurbits may be harvested on the day of the application of Acrobat. Read and follow the label directions. Effective cultural practices will minimize damage caused by Phytophthora blight. For more information on Phytophthora blight of cucurbits, click here.

Chemical control of Phytophthora blight of peppers has not been successful in Illinois. However, the results of our greenhouse and field trials in the past three years have shown that three cultivars (Paladin, Reinger, and Emerald Isle) are resistant to P. capsici isolates from Illinois. Planting resistant cultivars, with effective cultural practices, is recommended. Eggplants do not exhibit much blight, but severe fruit rot develops after rainfalls. Prevention of fruit contact with soil will reduce fruit rot of eggplants caused by P. capsici. For more information on Phytophthora blight of peppers, click here.