Alternaria burnsii

Fungal Disease

Cumin blight, caused by the fungus Alternaria burnsii, is the second most significant disease affecting cumin crops, after wilt. The disease is highly destructive, often appearing alongside wilt, and can cause severe damage, particularly at the flowering stage. Effective management relies on preventive and prophylactic measures.

1. Importance of Cumin Blight

• Pathogen: Alternaria burnsii.
• Economic Impact:
  • Can significantly reduce seed quality and yield.
  • Leads to the production of unmarketable seeds due to shriveling and poor seed maturity.
• Associated Diseases: Often co-occurs with wilt, amplifying damage.

2. Symptoms of Cumin Blight

• Initial Symptoms:
  • Dark brown spots appear on leaves and stems.
  • Leaf tips become necrotic, turning purple and eventually black.
• Progression:
  • Infection spreads to all above-ground parts, including stems.
  • Stem tips may bend downwards under severe infection.
• Seed Effects:
  • Seeds become shriveled and are easily lost during winnowing.

3. Disease Cycle

• Primary Source:
  • A. alternata is seed-borne and can cause seedling blight.
• Secondary Spread:
  • Conidia (fungal spores) survive under warm and dry conditions for several months.
  • Cloudy weather, especially after flowering, accelerates disease incidence.

4. Favorable Conditions for Disease Development

• Temperature:
  • Morning: 7.5–12.9°C.
  • Evening: 21–24°C.
• Humidity:
  • High relative humidity (91–95%).
• Weather:
  • Warm, humid conditions during the flowering stage.
  • Cloudy weather increases disease severity.

5. Impact on Crop

• Reduces seed maturity and size, leading to poor germination and marketability.
• Early sowing increases disease intensity and results in higher economic losses.

6. Management Strategies

A. Preventive Measures

1. Seed Treatment:
   • Treat seeds with fungicides or biocontrol agents to reduce seed-borne infections.
2. Cultural Practices:
   • Avoid early sowing to reduce disease risk.
   • Maintain optimal crop spacing to improve air circulation.

B. Weather Monitoring

• Track weather conditions to anticipate disease outbreaks and implement timely interventions.

C. Chemical Control

1. Prophylactic Sprays:
   • Fungicides like mancozeb, chlorothalonil, or copper-based fungicides can prevent disease spread.
   • Begin sprays at flowering stage and repeat at regular intervals if conditions remain favorable.
2. Seedling Protection:
   • Apply fungicides during early crop stages to protect against seedling blight.

D. Post-Harvest Management

• Ensure proper winnowing to remove infected seeds.
• Store seeds under dry, cool conditions to prevent fungal survival.

E. Resistant Varieties

• Encourage the development and use of cumin varieties resistant to blight.