Symptoms first appear as water-soaked, gray lesions that collapse and darken. Lesions turn velvety as spores are produced. Infection generally occurs at growth cracks, injuries or at the blossom-end of fruit. Internal colonization of pepper fruit without external signs of infection can occur when flowers are infected.
Anthracnose Fruit Rot (Ripe Fruit Rot)
Colletotrichum capsici, C. coccodes, C. gloeosporioides, C. acutatum
These fungi may infect the epidermis of immature fruit and remain latent until harvest. Symptoms usually develop on ripe fruit, giving this disease its common name: “Ripe Fruit Rot.” Fruit lesions first appear as small, indefinite, slightly sunken, water-soaked spots that may enlarge rapidly and coalesce. Later, fruiting bodies form in concentric circles to cover the surface of lesions. The lesions appear tan or brown and are covered with salmon to orange gelatinous spores. If the fruit rot extends to the seed cavity, it may infest and infect the seed.
Botrytis Fruit Rot (Grey Mold Rot)
Initial infection occurs when fruit are in direct contact with the soil. The fungus also colonizes dying flowers and fruit through the stem end, growth cracks and wounds. Botrytis also infects cold-injured fruit. Soft rot may develop and consume the fruit entirely. Affected areas are gray to olive green, slightly sunken and have distinct margins. The epidermis peels away easily from lesions to reveal softened, watery underlying tissue. Under humid conditions, gray-brown mycelia develop on the surface, and grape-like clusters of spores can be seen with a hand lens.
Phytophthora Fruit Rot
Phytophthora capsici, P. nicotianae var. parasitica
Phytophthora rot occurs when fruit are in contact with the soil or mycelia grows through the peduncle into the fruit. Infected fruit tissue is water-soaked and dark-green at first; later, white mycelium and sporangia develop on the surface of the affected area and, within several days, consume the entire fruit. In contrast to infected tomato fruit, no concentric rings develop. Fruit affected by these fungi dry rapidly and shrivel, but do not drop.
Contamination and wounding of fruit during the packing process is the primary means of infection. Symptoms first appear as soft, water-soaked lesions that are not discolored. Lesions develop from wounds, the stem end or inner walls, and quickly enlarge to engulf the entire fruit. When the epidermis ruptures, liquefied tissue is released. Under high humidity, profuse, coarse mycelia cover lesions. Later, white sporangia develop that turn black as they mature, giving a peppery, speckled appearance to the mycelia. In storage, these fungi penetrate directly from nests of infected fruit into adjacent healthy fruit.
Conditions for Disease Development
Rain splashes overwintering spores from soil and crop debris onto developing fruit. Symptom development is generally favored by high humidity. Botrytis fruit rot occurs during periods of cool, wet weather. The remaining four fruit rots occur during warm, wet weather.
Fruit injury during harvest and packing should be avoided. Improved sanitation in the field and in the packinghouse is effective at helping to reduce losses due to fruit rots. All harvest equipment, the packing line and packing boxes should be sanitized daily. Dumptank water and packing-line washers should maintain a minimum available chlorine concentration of 150 ppm at pH 6.0-7.5. Culling infected and injured fruit during packing help reduce losses due to post-harvest decays. Wet surfaces should be dried promptly before packing, and fruit should be cooled quickly to 10° C (50° F).