Cause Phytophthora capsici, a fungus-like microorganism. This soil-inhabiting organism causes root rot in pepper and eggplant and is most active in moist, warm weather (75°F to 91°F). Disease is generally seen in the wettest areas of a field.
Symptoms Dark-gray to dark-brown, water-soaked spots develop on roots and stems, causing plants to wilt and die. Leaf spots develop, which are initially gray-to-brown in color, water soaked in appearance, and irregularly shaped, later becoming light brown. Fruit show similar spots, often enlarging to cover the entire fruit, which later dries and mummifies. Whitish sporulation may develop on infected fruit.
Cultural control
- Plant in raised beds.
- Practice light irrigation to help prevent overly wet soil; sub-surface drip irrigation can help keep the soil surface dry and minimize disease development.
- Plant in well-drained areas of the field.
Chemical control
- Orondis Gold (Group 49 + 4) at 28 to 55 fl oz/A as an in-furrow, transplant water or banded soil application at planting. May be applied through drip after emergence. Preharvest interval is 7 days. 48-hr reentry.
- Regalia (Group P5) at 1 to 4 quarts/A plus another fungicide on 7- to 10-day intervals. Does not benefit from the addition of an adjuvant. Preharvest interval is 0 days. 4-hr reentry. O
- Ridomil Gold SL at 1 pint/A in a directed spray to the base of the plant after planting and a second application 30 days later. Mechanically incorporate or irrigate in. Do not apply within 7 days of harvest. 48-hr reentry.
- Warhammer (chitosan) at 4 to 12 fl oz/A on 7- to 14-day intervals. Studies at the University of Florida showed a reduction in disease severity for Phytophthora blight in squash when chitosan was applied as a 1% soil drench. No preharvest interval or reentry interval requirement.
Biological control Efficacy in the Pacific Northwest is unknown.
- Actinovate AG at 3 to 12 oz/A as a soil drench at planting. 4-hr reentry. O
- Actinovate Lawn & Garden at 0.5 to 1 teaspoon/gal water. H O
- Bexfond at 7 to 28 fl oz/A. O
- Double Nickel LC at 0.5 to 4.5 pints/A for soil application on 14- to 28-day intervals. Can be applied the day of harvest. 4-hr reentry. O
- Rootshield WP at 3 to 5 oz/100 gal water for greenhouse soil drench and field chemigation or at 16 to 32 oz/A as an in-furrow spray. 4-hr reentry. O
- Stargus at 6 to 8 fl oz per 1,000 ft row as an in-furrow treatment, or 3 to 4 quarts/A as a soil drench (drip or chemigation) on 10- to 21-day intervals. Preharvest interval is 0 days. 4-hr reentry. O
Reference Mo, X., and Zhang, S. 2013. Effect of chitosan, Heads Up and TiO2 on Phytophthora blight in squash, 2012. Plant Disease Management Reports 7:V081.