Leaf Spot of Turmeric

Causal Organism: Colletotrichum capsici
Sub-division: Deuteromycotina

Symptoms:

• On Leaves: Elliptic to oblong spots appear on both surfaces, predominantly on the upper surface.
• Spot Characteristics:
  • Grayish center with dark brown margins surrounded by a yellow halo.
  • Central portion becomes thin and papery.
  • Multiple spots coalesce, forming irregular necrotic patches.

Etiology:

• Primary Inoculum: Infected plant debris in the soil.
• Secondary Inoculum: Airborne conidia spread through wind and rain splash.
• Favorable Conditions:
  • Cool and humid weather.
  • Dense shading which increases humidity around the plants.

Disease Cycle:

• Primary Infection: Initiated by conidia present in infected plant debris from the previous season.
• Secondary Infection: Airborne conidia infect healthy leaves under favorable conditions.
• The pathogen survives in plant debris, leading to new infections each season.

Management:

• Cultural Practices: Remove and destroy infected plant debris to reduce primary inoculum. Avoid excess shading to decrease humidity around plants.
• Rhizome Treatment: Treat rhizomes with Copper oxychloride @ 0.25% solution before planting.
• Foliar Spray:
  • Carbendazim + Mancozeb @ 0.2% spray during August to December to prevent and control infection.
• Resistant Varieties: Use tolerant varieties such as TS-2, TS-4, TS-9, and TS-8.