Powdery mildew is a polycyclic fungal disease affecting redgram, capable of causing repeated infections and secondary spread. It thrives in cool, humid climates for infection and warm, humid conditions for sporulation. The disease is more severe in Indian redgram varieties with thin, succulent leaves compared to Kenyan varieties with thicker leaves.

Epidemiology

• Optimal Conditions: Develops at temperatures of 20–35°C, with 25°C being ideal.
• Sources of Inoculum: Perennial pigeonpeas, volunteer plants in shaded areas, ratoon growth, and infected plant parts harbor the fungus.
• Disease Spread: Early sowing and irrigation in India encourage disease establishment. Plants affected by sterility mosaic or phyllody often act as reservoirs due to prolonged green periods.

Symptoms

• Initial Signs: Small chlorotic spots appear on the upper leaf surface, followed by white powdery patches on the lower surface.
• Progression: As the fungus sporulates, white powdery growth covers the entire lower leaf surface, flowers, and pods.
• Severe Infections: Result in heavy defoliation, stunting, and reduced plant vigor, impacting yield.

Effective management includes timely sowing, avoiding susceptible varieties, and controlling the disease during its early stages to minimize spread and impact.