Rhizoctonia

Rhizoctonia (Rhizoctonia solani) is a devastating soil-borne fungal pathogen belonging to the phylum Basidiomycota. It is a filamentous fungus that lacks asexual spores, relying on sclerotia and mycelial fragments to survive in the soil and on host debris for several seasons. Its wide host range makes it one of the most significant threats in modern agronomy.

The fungus causes a variety of diseases globally, collectively referred to as rhizoctonia diseases. Major crops affected include potatoes (black scurf), sugar beets, cereals, turfgrass, and many vegetables like tomatoes and beans. The primary symptoms involve damping-off, root decay, brown lesions on stems, and necrosis of the crown tissue, which often kills young seedlings.

The infection cycle begins when sclerotia germinate in response to chemical signals from the roots of host plants. The mycelium grows through the soil and penetrates the plant tissue either through wounds or direct pressure using infection structures known as infection cushions. The pathogen thrives in high-moisture environments with temperatures ranging from 15°C to 25°C, making early spring planting particularly risky.

The economic impact of Rhizoctonia solani is severe, resulting in significant yield losses and reduced crop quality. In potato production, for instance, the presence of sclerotia on the tuber surface downgrades the product's market value, while in grain production, the pathogen causes stunted growth and severe root damage, leading to lodging and reduced grain fill.

Effective management requires an integrated pest management (IPM) strategy. Key practices include the use of fungicide-treated seeds and tubers, maintaining proper crop rotation to break the pathogen's life cycle, and improving soil drainage. Furthermore, biological control agents such as Trichoderma species have shown promise in suppressing the pathogen's growth and protecting the root zone.