Black scurf/ canker(Rhizoctonia solani)

Symptoms

• The disease commonly affects various parts of the potato plant, including tubers, sprouts, stems, and stolons.
• A prevalent symptom is the presence of black scurf, appearing as dark brown to black irregular lumps firmly attached to the tuber surface.
• These lumps adhere closely to the tuber and are difficult to wash off.
• Additional tuber symptoms include skin cracks, crater-like depressions, pitting, stem-end necrosis, and shape deformities.
• Sprout injury is a common occurrence, both in storage and in fields post-planting, characterized by tissue discoloration.
• Heavily infected sprouts may fail to emerge from the soil, leading to patchy germination.
• Emerging sprouts may develop cankers, causing the girdling of stem bases, resulting in upward rolling of leaves with pinkish or purplish margins.
• Often, small green or reddish aerial tubers form in the axils.
• The infection can also spread to roots and developing stolons, leading to rotting of cortical tissues.
• Infected roots may subsequently shed, resulting in plants with poor root systems, while infected stolons produce deformed tubers.

Management

• Utilizing treated seed continuously over 2-3 crop seasons has been observed to effectively control the disease.
• Implementing crop rotation with maize or 'dhaincha' (Sesbania aegyptiaca) for green manure aids in suppressing disease buildup.
• Planting disease-free and healthy tubers proves beneficial in reducing disease incidence.
• Employing a rotation schedule of two to four years with cereals, brassicas, and legumes aids in disease management.
• Increasing the organic matter content in soil helps diminish fungus populations by enhancing the activity of antagonist microorganisms.
• Proper disposal of crop debris is essential for disease control.
• Prudent use of fertilizers is recommended for disease management.
• Implementing good drainage, shallow planting depths, and weed eradication practices contribute to disease reduction.
• Seed tuber treatment with Trichoderma viride or Pseudomonas fluorescens (20gm/L of water)
• Seedling dips in Trichoderma viride or Pseudomonas fluorescens (20gm/L of water) reduces the disease.
• Soil Application of Trichoderma viride or Pseudomonas fluorescens multiplied in neemcake and organic manure also reduces incidence of the disease.

Chemical Control

Extremely Toxic

Highly Toxic

Moderately Toxic

Slightly Toxic