Diplodia stem rot of pigeon pea

The fungus Diplodia cajani is the primary pathogen responsible for stem rot in pigeon pea (Cajanus cajan). This fungus causes significant damage to the plant's vascular and structural tissues, potentially leading to the death of affected stems and reducing overall agricultural yield.

Pigeon pea is the specific host for this pathogen. While it primarily affects stems, it can also manifest on the pods and seeds under high humidity conditions. The disease is particularly prevalent in regions where climatic conditions remain consistently humid throughout the growing season.

The visual symptoms typically include the development of darkened, water-soaked, or necrotic lesions on the stem surface. As the infection progresses, the tissues become necrotic, and the formation of pycnidia — small, black, flask-shaped structures — becomes visible to the naked eye.

The spread of Diplodia cajani is facilitated by moisture and temperature levels that support sporulation. Spores are dispersed through wind and splashing rain, allowing the infection to spread rapidly within a field if density is high and air circulation is poor.

Integrated pest management strategies are crucial for controlling this disease. Effective control involves a combination of cultural practices, such as crop rotation, deep tillage to bury infected stubble, and the application of fungicides during critical growth stages to prevent severe outbreaks.

• Selecting resistant varieties of pigeon pea.
• Proper disposal of crop debris after harvest.
• Seed treatment to eliminate initial inoculum.
• Improving soil drainage to reduce humidity.