Several species of plant pathogenic fungi in the genus Colletotrichum cause anthracnose in peppers and many other vegetables and fruits. Until the late 1990s, anthracnose of peppers and tomatoes was only associated with ripe or ripening fruit. Since that time, a more aggressive form of the disease has become established. This form attacks peppers at any stage of fruit development and may threaten the profitability of pepper crops in areas where it becomes established. This disease can also affect tomatoes, strawberries, and possibly other fruit and vegetable crops.
Circular or angular sunken lesions develop on immature fruit of any size. Often multiple lesions form on individual fruit. When disease is severe, lesions may coalesce. Often pink to orange masses of fungal spores form in concentric rings on the surface of the lesions. In older lesions, black structures called acervuli may be observed. With a hand lens, these look like small black dots; under a microscope they look like tufts of tiny black hairs. The pathogen forms spores quickly and profusely and can spread rapidly throughout a pepper crop, resulting in up to 100% yield loss. Lesions may also appear on stems and leaves as irregularly shaped brown spots with dark brown edges.
This form of pepper anthracnose is caused by the fungus Colletotrichum acutatum. The pathogen survives on plant debris from infected crops and on other susceptible plant species. The fungus is not soil-borne for long periods in the absence of infested plant debris. The fungus may also be introduced into a crop on infested seed. During warm and wet periods, spores are splashed by rain or irrigation water from diseased to healthy fruit. Diseased fruit act as a source of inoculum, allowing the disease to spread from plant to plant within the field. The fungus survives in and on seeds. Anthracnose is introduced into the field on infected transplants or it can survive between seasons in plant debris or on weed hosts. Alternative hosts include weeds and other plants in Solanaceae (tomato, potato, eggplant) although infections of these hosts are extremely rare in Florida. Fruit are infected when spores of the fungus or infested debris is rain splashed onto pepper plants. New spores are produced within the infected tissue and then are dispersed to other fruit. Workers may also move spores with equipment or during handling of infected plants. Infection usually occurs during warm, wet weather. Temperatures around 80° F (27° C) are optimum temperatures for disease development, although infection occurs at both higher and lower temperatures. Severe losses occur during rainy weather because the spores are washed or splashed to other fruit resulting in more infections. The disease is more likely to develop on mature fruit that is present for a long period on the plant, although it can occur on both immature and mature fruit. Anthracnose can infect from 15 °C to 30°C. But a long leaf wetness is needed to fullfil the needs for an infection. At optimum temperature from 20°C to 25°C still 12 hours of leaf wetness are needed. Higher or cooler temperature will need even longer leaf weetness periods (no linear function/array needed for calculation). Fieldclimate calculates the possilbe infection events on base of leaf wetness and the temperatures during this event.