Rhizoctonia

Rhizoctonia is a severe soil-borne disease caused by fungi of the Rhizoctonia spp. group, primarily Rhizoctonia solani. This pathogen affects a wide variety of crops including onions, garlic, anemone, celery, peanuts, asparagus, oats, and forage beet. The fungus survives in the soil as sclerotia and mycelium, waiting for favorable conditions to infect the roots and lower stems of developing plants.

Symptoms of Rhizoctonia typically manifest as root rot, damping-off, and stem lesions. Infected tissues turn dark brown or black, showing distinct sunken ulcers. On bulbs and tubers, the fungus often appears as dark, scabby sclerotia that adhere to the surface. As the infection progresses, the vascular system is compromised, resulting in wilting, chlorosis, and the eventual collapse of the affected plant.

Environmental conditions such as high soil moisture and moderate temperatures (around 15°C to 20°C) are critical for the development of the disease. Compacted soils with poor drainage provide a perfect environment for the fungus to multiply. Since the pathogen is soil-borne, it can spread through infested agricultural equipment, contaminated irrigation water, and the movement of infected soil from one field to another.

The economic impact of Rhizoctonia is significant, particularly in commercial farming. It leads to poor crop stand density, reduced seedling vigor, and substantial losses in yield quality. In storage, infected produce is prone to secondary infections, which further degrades the marketability of crops such as onions and root vegetables, leading to high financial losses for producers.

Effective management requires an integrated approach. Crop rotation with non-host species is essential to break the pathogen's life cycle. Soil preparation, including improving aeration and correcting pH levels, helps create conditions unfavorable for fungal growth. Chemical control involves the use of specialized seed treatments and soil-applied fungicides to suppress initial inoculum levels during the critical stages of plant emergence.

• Implement long-term crop rotation.
• Use certified disease-free seeds.
• Improve soil drainage and aeration.
• Apply targeted fungicides.
• Sanitize farming equipment.