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Phytophthora Blight and Its Management in Cucurbit Crops and Other Vegetables

Margaret Tuttle McGrath
Department of Plant Pathology
Long Island Horticultural Research and Extension Center, Cornell University
3059 Sound Avenue, Riverhead, NY 11901;
mtm3@cornell.edu

Phytophthora blight is one of the more destructive diseases of vegetable crops. Most cucurbit crops and pepper are very susceptible. Cantaloupe is less commonly affected than other cucurbits. Eggplant, tomato, snap bean, and lima bean are also susceptible. Snap bean is the most recently identified host for the pathogen. There are several articles posted under Beans.

Symptoms include crown rot, stem and vine lesions, tip blight, leaf spots, lesions on petioles, root rot, and fruit rot. Type of symptoms that occur vary among crops. Fruit rot is typically the only symptom with cantaloupe, cucumber and tomato.

There are photographs of symptoms at several Cornell websites:

The pathogen causing Phytophthora blight, Phytophthora capsici, is thought to move into a field primarily in contaminated water or soil moved from an affected field. It can infect seed. This pathogen can survive in a field for many years in the absence of a host crop as oospores or by infecting roots of weeds including purslane, thus it is difficult to manage through rotation.

Recommended management program includes cultural practices combined with fungicides. It is considered key to minimize opportunity for there to be standing water in a field after rain or irrigation as this provides ideal conditions for blight to develop. A preventive fungicide program is recommended.

Detailed information about Phytophthora blight and its management are in the following articles and tables:

Webpage created July 2017.