In dry areas, the infection is generally visible on the plant’s roots and crowns. A distinctive black or brown lesion appear on stems at the soil line. At high relative humidities, all parts of the plant are affected. Infected roots become dark brown and mushy, and cause damping-off of seedlings. Dark green to brown water-soaked spots appear on leaves and fruits. Mature plants show symptoms of crown rot. Dark brown lesions enclose the stem and result in plant death. Fruits rot on the field, after harvest, or during storage.
Phytophthora capsici is a soilborne pathogen that can stand extreme environmental conditions. It can survive in plant debris on alternative hosts or in the soil itself for up to three years. It is later dispersed by irrigation or surface water. P. capsici grows at temperatures between 7°C and 37°C, around 30°C is optimal. Under ideal conditions of elevated temperature and high humidity, the disease can progress very rapidly. Cooler temperatures limit the spread of the disease.
The bacterium Burkholderia cepacia (MPC-7) has been tested positively for its antagonist effect against Phytophthora capsici.
Always consider an integrated approach with preventive measures together with biological treatments if available. Products containing mefenoxam applied as spray at planting, and complemented with a fixed copper fungicide two weeks after, will prevent infection during the foliar phase of the disease. Mefenoxam can also be used in drip irrigation systems to limit the damage to fruits when symptoms of crown rot are visible.