Botrytis Blight of Marigold

Causal Organism: Botrytis cinerea
Sub-division: Deuteromycotina

Symptoms:

• Flower parts become necrotic (brown/black) and die.
• Gray, fuzzy mold develops on dead tissue under humid conditions.
• Infected blossoms wilt, wither, and drop prematurely.
• Occasionally, brown lesions may appear on leaves and stems.

Disease Cycle:

• Primary Infection: By infected flowers or plant debris.
• Secondary Infection: Airborne conidia (spores) spread to healthy plants.
• Survival: As sclerotia (hardened fungal structures) or mycelium in debris.

Favorable Conditions:

• High humidity (>90%) and temperatures of 15-23°C.
• Prolonged wetness from rain or overhead irrigation.
• Dense planting and poor air circulation.

Management:

Cultural Practices:

• Remove and destroy dead plant parts.
• Avoid overhead irrigation; use drip irrigation instead.
• Space plants properly for good air circulation.

Chemical Control:

• Copper Oxychloride @ 0.3% as a preventive spray.
• Alternate fungicides (e.g., Chlorothalonil, Mancozeb) to prevent resistance.

Biological Control: Use antagonistic microorganisms like Trichoderma spp. and Bacillus subtilis.

Integrated Disease Management (IDM): Combine cultural, chemical, and biological controls for effective management.