Brown rot

Monilinia fructigena is a significant fungal pathogen belonging to the order Helotiales and family Sclerotiniaceae. It is the primary causal agent of brown rot, a devastating disease that affects a wide variety of fruit-bearing trees, particularly pome fruits like apples, pears, and quinces. This pathogen causes extensive damage worldwide, leading to pre-harvest fruit decay and post-harvest storage losses.

The disease primarily manifests as fruit rot, where infected areas turn brown and soft. As the infection progresses, concentric circles of tan-colored spore tufts develop on the surface of the fruit skin. Infected fruits often shrivel and turn into dark, mummified remains. These mummies are the primary source of overwintering inoculum for the fungus, as they can persist on the tree branches or fall to the orchard floor.

The life cycle of the pathogen is driven by environmental conditions. During the spring and summer, moisture triggers the release of conidia, which are then disseminated by wind, rain splashes, and insects. Infection typically requires an entry point on the fruit, such as skin punctures caused by insects (e.g., codling moth), hail damage, or small cracks. Once established, the fungus grows rapidly, consuming the fruit tissue and spreading to adjacent healthy fruit through direct contact.

Optimal development of brown rot occurs in warm and humid climates. Temperatures between 15°C and 25°C, combined with high humidity or frequent rainfall during the fruit ripening stage, create ideal conditions for rapid disease spread. In dense orchard canopies, lack of air circulation significantly increases the risk of infection, as the fruit remains moist for longer periods.

Effective management and control strategies involve an integrated approach to maintain orchard health:

• Rigorous sanitation: Collecting and destroying all infected or mummified fruit from the orchard.
• Pruning: Improving canopy aeration and light penetration to reduce humidity around fruit.
• Pest control: Managing insect populations that cause physical injuries to the fruit skin.
• Fungicide applications: Using appropriate chemical sprays during critical growth stages and before harvest.
• Post-harvest handling: Implementing strict hygiene and low-temperature storage to prevent secondary spread.