Phytophthora blight typically develops in low-lying areas of fields after a heavy rain and can spread quickly throughout the entire field.
Planting on a ridge or raised, dome-shaped bed will help provide better soil drainage. Use a minimum 3-year crop rotation with crops other than pepper, cucurbit, lima and snap beans, eggplant, or tomato. In fields with low-lying or wet areas, plant only Phytophthora-resistant/tolerant bell pepper cultivars such as ‘Paladin’, ‘Aristotle’, ‘1819’, ‘Intruder’, ‘Archimedes’, or ‘Revolution’. In heavily-infested fields with a known history of Phytophthora blight, plant only tolerant cultivars to help reduce plant losses. If mefenoxam-insensitivity is known to exist in a field/farm, plant only tolerant cultivars. Do not apply mefenoxam or metalaxyl in fields where insensitivity is known to exist.
For control of the crown rot phase of Phytophthora blight, apply:
mefenoxam–1.0 pt Ridomil Gold 4SL/A or 1.0 qt Ultra Flourish 2E/A or metalaxyl (MetaStar)–4.0-8.0 pt 2E/A at transplanting and 30 days later, or
Presidio (fluopicolide, 43) at 3.0-4.0 fl. oz 4SC/A at transplanting and/or 14 days later (between two mefenoxam applications),
Ranman (cyazofamid, 21) at 2.75 fl oz 400SC at transplanting (Ranman may be added to transplant water, see label for restrictions) and/or 14 days later (between two mefenoxam applications)
Phosphite materials (FRAC code 33) such as Rampart, ProPhyt, K-Khite may also be tank mixed with one of the above to help suppress Phytophthora blight
Growers with a known history of mefenoxam-insensitivity on their farm should use Presidio or Ranman plus a Phosphite fungicide in rotation. If mefenoxam has not been used in particular fields on any crop for a number of years (more than 5+) the fungus may revert back to being mefenoxam-sensitive.
Recommendations for Organic Practices
Organic bell pepper growers with a history of the Phytophthora blight should plant cultivars that have resistance or tolerance to the disease. Long non-host crop rotations are critically important for organic production. Regular applications of Double Nickel (Bacillus amyloliquefaciens) or Regalia (Extract of Reynoutria sachalinensis) as drenches or via the drip system prior to the onset of disease may help suppress Phytophthora blight development.