Bacterial necrosis of papaya

Pathogen and disease type. Bacterial necrosis of papaya is caused by the bacterium Erwinia papayae. It is a severe vascular disease that systemic attacks all above-ground organs of the plant. As a gram-negative pathogen, it disrupts the internal tissues of the host, leading to rapid necrosis and soft rot symptoms.

Affected crops and damage. The disease primarily affects papaya (Carica papaya). It is considered a devastating phytopathological problem in tropical and subtropical regions. The economic impact is significant, as the infection can wipe out large portions of plantations, causing wilting of the main stem, fruit rot, and complete mortality of the plants.

Symptoms and signs. The disease is characterized by water-soaked spots on leaves that rapidly turn into dark necrotic areas. On the stem, sunken lesions or ulcers appear, often oozing bacterial fluid. As the disease progresses, the terminal shoot begins to blacken and die back, while fruits become covered in watery lesions and eventually drop prematurely.

Conditions for development and spread. The bacterium thrives in high-humidity environments and temperatures ranging from 25°C to 30°C. Spread occurs primarily through splashing rain, irrigation water, and contaminated tools used during pruning or harvesting. The pathogen can also survive in decaying plant debris, providing an inoculum source for the next crop.

Control and prevention measures. Since there is no effective curative treatment for infected plants, management strategies focus on preventing the introduction and spread of the pathogen. Recommended practices include:

• Planting only certified, disease-free seeds and seedlings.
• Rigorous monitoring and immediate rogueing of infected plants from the field.
• Sanitizing pruning tools with bleach or alcohol after working on each individual plant.
• Improving field drainage to reduce humidity levels around the crops.
• Managing insect populations to minimize mechanical damage that serves as entry points for bacteria.