Disease guide

Worldwide, in tropical and subtropical areas

This fungus attacks seedlings soon after emergence. Dark-brown lesions develop on the stem above the soil line. Eventually, a dry rot or canker girdles the stem and the seedling collapses and dies. When older plants are infected, circular or irregular gray to brown lesions develop on lower leaves and stems. Lesions enlarge and coalesce, causing complete yellowing of foliage and severe defoliation. Cankers on stems can cause wilting and death of the upper plant. Fruit lesions start as soft, light-brown, sunken oval areas. Later, fruit lesions deepen, enlarge and coalesce to develop a soft, spongy rot. In dry weather, fruit may shrink and mummify. A diagnostic characteristic is the minute black fruiting bodies (pycnidia) that develop in a circular pattern in the center of mature lesions. Pycnidia are the inoculum source for later infections.

This fungus can survive in plant debris or in mummified fruit in the soil. Infection may occur when rain or overhead irrigation splash inoculum to foliage and stems. Seed produced on plants grown in affected fields can be infested with fungal spores and may initiate disease on seedlings. Phomopsis blight is generally favored by hot, wet weather.

Sow high-quality seed to help produce pathogen-free transplants. Remove and destroy all infected plant material, and establish a crop rotation to break the disease cycle. Mulch and furrow irrigate to help reduce splashing of water and soil. A regular schedule of protectant fungicide sprays may reduce damage in areas where the disease is known to occur.