Sclerotium rolfsii

Fungal Disease

Sclerotium rolfsii

Fungal Disease

Sclerotium rolfsii

Fungal Disease

Sclerotium rolfsii

Fungal Disease

Sclerotium rolfsii

Fungal Disease

Southern blight, caused by the soil-borne pathogen Sclerotium rolfsii, poses a significant threat to capsicum (bell pepper) crops, particularly in warm and humid conditions. Below is a pointwise overview of the disease, its symptoms, and management strategies.

1. Optimal Conditions for Growth

• Temperature: Hyphal growth occurs between 8-40ºC, with optimal growth and sclerotia production at 27-35ºC.
  
• Moisture: Requires water-saturated soil for hyphal growth and sclerotia germination; high humidity also favors fungal development.

2. Symptoms

• Initial Wilting: The first noticeable symptom is wilting of the plant.
• Stem Blight: A brown blighted section appears at the collar region of the stem.
• Progression: As the disease advances, the plant continues to wilt, and leaves turn brown.
• Fruit Susceptibility: The destruction of the canopy increases fruit vulnerability to sunscalding.
• Visible Mycelial Growth: A white mycelial mat may develop on the stem and surrounding soil, with mature sclerotia appearing as light tan to dark brown structures that eventually fall off.

3. Disease Impact

• Field Distribution: Damage tends to be spotty rather than uniform across fields; only specific areas may be severely affected.
• Economic Losses: Estimated global losses due to Sclerotium rolfsii range from 10 to 20 million dollars, with yield reductions between 1% and 60% in affected fields.
• Host Range: Common hosts include legumes, crucifers, and cucurbits, indicating a broad impact on various crops.

4. Pathogen Characteristics

• Survivability: Sclerotia can survive harsh climatic conditions, making Sclerotium rolfsii a persistent threat for subsequent growing seasons.
• Spread: Primary inoculum (sclerotia) can be disseminated by wind, water, animals, and soil.

5. Management Strategies

• Exclusion: Preventing the introduction of the pathogen into the growing area.
• Cultural Practices: Implementing crop rotation and using resistant or transgenic plant varieties.
• Physical Control: Plant removal, soil removal, and solarization to kill pathogens in the soil.
• Chemical Treatments: Soil treatment with fungicides, although effectiveness may vary.
• Integrated Approaches: Combining multiple strategies to improve control and mitigate the impact of the disease.

Despite ongoing research into managing southern blight, it remains a challenging pathogen for capsicum growers, necessitating a multifaceted approach to control and reduce its impact on crop yield.