Bull's-eye rot fungus

Neofabraea perennans is an ascomycete fungus within the order Helotiales, widely recognized in plant pathology as the primary agent of bull's-eye rot. This pathogen is a significant threat to orchard productivity, specifically affecting apple and pear trees by colonizing both the bark and the harvested fruit.

The fungus is characterized by its ability to cause perennial cankers on branches and tree trunks. These lesions are focal points for the fungus, allowing it to persist in the orchard environment from year to year. In addition to woody tissue damage, the pathogen infects ripening fruit, leading to sunken, firm, and often light-colored rot spots that develop during storage.

The life cycle of Neofabraea perennans is highly dependent on humidity and temperature. The fungus overwinters in the margins of the bark cankers. Conidia are produced during cool, wet periods in the spring and autumn and are disseminated primarily by rain splashing. Fruit infection usually occurs in the orchard before harvest, often through lenticels, but symptoms remain latent until fruit enters cold storage.

Environmental conditions that favor the spread of this pathogen include high levels of rainfall and moderate temperatures during the late growing season. Neglected orchards with heavy canopy density, poor aeration, and unpruned infected limbs are at a much higher risk of epidemic outbreaks. Stress factors, such as drought followed by excess moisture, can further exacerbate susceptibility.

Effective control requires an integrated approach to orchard management. Key strategies include:

• Thorough pruning and removal of infected wood to reduce inoculum sources.
• Application of specialized fungicides before harvest to protect developing fruit.
• Optimizing orchard hygiene to promote air circulation.
• Rapid cooling and controlled atmosphere storage to inhibit post-harvest lesion development.