Methods for Managing Phytophthora Blight (Phytophthora capsici) of Pepper

Phytophthora blight, caused by Phytophthora capsici, is one of the most important diseases of peppers worldwide, causing yield losses of up to 100%. The pathogen can infect plants at all growth stages. P. capsici infects roots, crowns, stems, leaves, and fruit, causing seedling damping-off, stem lesion, stem blight, leaf spot, and fruit rot. The first symptom on pepper in the field is commonly crown rot. A lesion girdling the base of the stem causes rapid collapse and death of the plant. The affected plants usually die within few days. In some cultivars only fruit are infected. Infected fruit develop dark, water-soaked lesions, which are commonly covered with white mycelium of the pathogen. Three approaches, (i) using resistant cultivars, (ii) induction of resistance in plants by red-light treatment, and (iii) application of fungicides, were evaluated for management of Phytophthora blight in peppers. To identify resistant pepper cultivars to P. capsici, more than 80 cultivars/accessions of bell pepper were tested in the greenhouse and field. In the greenhouse, 8-week-old seedlings were inoculated with P. capsici. Pepper cultivars were also evaluated in naturally infested commercial fields with P. capsici. Cultivars, Aristatol, Declaration, Emerald Isle, Paladin, Reinger, Revolution, Seigers 9915776, and Snapper F1 were resistant to isolates of P. capsici. Pepper seedlings grown under red light (600-700 nm) for four weeks reduced P. capsici-infection by 74% in the greenhouse, but the treatment failed to provide a season-long protection against P. capsici in the field. More than 40 fungicides were evaluated for their effectiveness for control of Phytophthora blight in the fields. Cyazofamid (Ranman 400SC), dimethomorph (Forum 4.16 SC), famoxadone + cymoxanil (Tanos 50WDG), mandipropamid (Revus 2.09SC), and mefenoxam (Ridomil Gold Copper 65WP) were effective in controlling P. capsici in pepper in the fields in. Applications of the fungicides should be at weekly intervals, beginning transplanting seedlings in the field until 3-4 weeks before the final harvest.