Measures to Control Rhizopus head rot in Sunflower Crop

Rhizopus head rot, caused by the fungus Rhizopus oryzae, is a potentially destructive disease of sunflowers, although its occurrence is sporadic. It can affect sunflowers grown for both oilseed and confectionery purposes.

• Type of Infestation: Fungal Disease
• Common Name: Rhizopus head rot
• Causal Organism: Rhizopus sp
• Affected Parts Of the plant: Flower Head, Seed and Stalk

• Temperature & Humidity: High temperatures (above 25°C) and high relative humidity (above 80%) favor infection and disease development. This is because these conditions create a moist environment that allows the fungal spores to germinate and grow easily.

• Initial: Look for brown, irregular, water-soaked spots on the back of the ripening head, usually near the flower stalk.
• Progression: These spots enlarge and become soft and pulpy, covered by a white, superficial mycelium that later turns black.
• Later stages: The infected head may dry prematurely, shrivel, and appear shredded. You might also observe coarse, thread-like mycelial strands within the shredded tissues.
• Spores: Small, black dots (sporangia) appear on the affected head, filled with spores that can be easily released and spread by wind to infect other plants.