Fusicoccum parvum

Fusicoccum parvum is a fungal pathogen known for causing cankers and dieback in various fruit and nut trees, including grapevines, citrus, stone fruit trees, and avocado. The disease it causes is often referred to as Botryosphaeria or Bot Canker.

1. Symptoms:

• Cankers: Fusicoccum parvum infects branches and trunks, leading to the formation of sunken and often elliptical cankers.
• Dieback: Infected branches may experience dieback, where the foliage at the tips wilts and dies.
• Fruit Symptoms: On some hosts, such as grapes, the pathogen can also cause fruit rot.

2. Disease Cycle:

• Infection: The fungus enters the host through wounds, such as pruning cuts or injuries caused by adverse weather conditions.
• Spore Production: The fungus produces conidia that are spread by rain, wind, or physical contact.
• Spread: Rain splash and irrigation water can contribute to the spread of the pathogen.
• Overwintering: The fungus can survive in infected plant tissues, providing a source of inoculum for the next growing season.

3. Identification:

• Canker Characteristics: Identifying cankers with sunken, elliptical shapes on branches and trunks is a key feature.
• Conidia: Microscopic examination may reveal the presence of conidia, aiding in accurate identification.

4. Management:

• Pruning Practices: Prune infected branches during dry periods, making clean cuts to remove infected tissues.
• Fungicide Applications: Fungicides may be applied during the dormant season as a preventive measure.
• Sanitation: Remove and destroy infected plant material to reduce the source of inoculum.
• Resistant Varieties: Where available, planting resistant varieties can be an effective strategy.

5. Importance:

• Economic Impact: Fusicoccum parvum can cause economic losses due to reduced yield, quality, and vitality of affected trees and crops.
• Global Distribution: The pathogen is present in various regions where susceptible host plants are grown.

6. Integrated Pest Management (IPM):

• Cultural Practices: Implement cultural practices that promote overall plant health, including proper irrigation, nutrient management, and avoiding unnecessary wounds.
• Monitoring: Regularly monitor plants for symptoms, especially during periods conducive to disease development.
• Fungicide Resistance Management: If using fungicides, follow recommended application practices to reduce the risk of fungicide resistance.