Updated August, 2023.
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.
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.
View symptoms in several crops at the LIHREC website where there is also information about Phytophthora blight and its management:
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:
- Phytophthora Blight (brief factsheet)
- Phytophthora Blight of Cucurbits (includes management information pertinent to other crops)
- Biopesticides for Organic Management of Phytophthora Blight
- Reduced tillage for Managing Phytophthora Blight and Other Soil-Borne Pathogens
- Biofumigation for Managing Phytophthora Blight and Other Soil-Borne Pathogens
- Fungicides for Managing Phytophthora Blight in Cucurbits and Other Vegetables
- Mobile Fungicides for Managing Three Major Cucurbit Diseases: Powdery Mildew, Downy Mildew, and Phytophthora Blight
More information:
- Phytophthora capsici, 100 Years Later: Research Mile Markers from 1922 to 2022. Published in the journal Phytopathology Nov 2022.
- Phytophthora Field Scouting Guide. Published in Growing Produce.
More information/prepared by:
Margaret Tuttle McGrath
Associate Professor
Long Island Horticultural Research and Extension Center (LIHREC)
Plant Pathology and Plant-Microbe Biology Section
School of Integrative Plant Science
College of Agriculture and Life Sciences
Cornell University
mtm3@cornell.edu