Sclerotium rot

Sclerotium rot is a destructive soil-borne fungal disease caused by pathogens of the genus Sclerotium, most notably Sclerotium rolfsii. This fungus acts as a necrotrophic pathogen, attacking the stems, roots, and sometimes the fruit of a vast array of plant species, causing rapid decay and systemic collapse.

The host range of Sclerotium species is exceptionally broad, affecting over 500 different plant species including legumes, vegetables, fruits, and nursery ornamentals. Its ability to survive for years in the soil as sclerotia makes it a persistent challenge for farmers and growers globally, especially in tropical and subtropical climates.

Symptoms often appear as a sudden wilt, typically accompanied by white, fan-like mycelial mats spreading across the soil surface and the lower stem. As the disease progresses, the stem tissues rot, turn brown, and become shredded. The most diagnostic sign is the presence of small, spherical, mustard-seed-like bodies known as sclerotia, which harden and darken as they mature.

The development of the disease is heavily dependent on moisture and temperature. It thrives in warm, humid environments where the soil is moist. Sclerotia serve as the primary inoculum, spreading through contaminated soil, irrigation water, and infected plant debris, making long-distance dispersal relatively common in agricultural settings.

Effective management requires an integrated approach. Cultural practices such as crop rotation with non-host species, improving soil drainage, and removing infected plant materials are essential. Biological control using beneficial fungi like Trichoderma species has proven effective in suppressing the pathogen's growth in the soil, while chemical fungicides may provide short-term relief during outbreaks.