Rhizoctonia

Rhizoctonia, triggered by the fungus Hypochnus cucumeris (widely known as Rhizoctonia solani), is a devastating soil-borne plant pathogen belonging to the Basidiomycota division. Unlike many other fungi, it lacks traditional conidia formation, relying instead on its vegetative hyphae and survival structures, called sclerotia, to persist in the environment and infect a broad range of agricultural crops.

This pathogen is responsible for various diseases, including stem canker, black scurf on potatoes, and damping-off in seedlings of vegetables and ornamentals. The damage is particularly severe on tubers and root crops, where the fungus causes deep lesions and rot, leading to poor plant establishment, stunted growth, and significant yield reduction. In grain crops, it can destroy the root system, causing nutritional deficiencies and premature death.

The biology of Hypochnus cucumeris involves a dormant phase where it survives as sclerotia in the soil or on plant debris. When environmental conditions, specifically high soil moisture and moderate temperatures, become favorable, these sclerotia germinate. The hyphae then colonize the surface of host roots or stems, penetrating the epidermis and parenchyma tissues to extract nutrients and degrade cell walls.

The spread of the disease is highly correlated with environmental factors. Rhizoctonia thrives in cool, moist soils, which is why early-season planting often leads to higher disease incidence if the soil remains cold. Poor soil drainage and compaction create anaerobic micro-environments that inhibit root growth while simultaneously favoring the rapid vegetative growth and spread of the fungal pathogen.

Effective management strategies require an integrated approach involving cultural, chemical, and biological controls. Key measures include the use of high-quality, certified disease-free seeds and tubers, implementing crop rotation cycles that break the pathogen's life cycle, and optimizing soil health through proper tillage and fertility management. Fungicide seed treatments are considered a standard and highly effective practice for early-season protection.

• Utilizing disease-resistant crop varieties.
• Improving soil aeration and drainage.
• Seed treatment with appropriate fungicides.
• Biological control using Trichoderma-based products.