Bull's eye rot

Bull's eye rot, caused by the fungus Neofabraea malicorticis, is a devastating disease affecting pome fruit trees, especially apples. This pathogen is primarily known for causing perennial cankers on the bark of trunks and branches, which can significantly weaken or even kill the affected tree over time if left untreated.

The characteristic symptoms of this disease include the formation of small, circular, reddish-brown depressed spots on the bark. As the infection progresses, these spots expand into elliptical cankers, often surrounded by a callus roll. In moist conditions, creamy-colored fruiting bodies emerge from the center of these lesions, serving as the primary source for further spread of the fungus.

The pathogen thrives in cool, wet environments, making late autumn and winter periods particularly high-risk for tree infection. Spores are disseminated by splashing rain and wind, entering the tree through pruning wounds, natural cracks in the bark, or injuries caused by frost. Once inside, the fungus colonizes the inner bark and cambium layers.

The impact of this disease is significant, as it interferes with the plant's vascular system, causing branch dieback and reduced vigor. In addition to bark damage, Neofabraea malicorticis is a major cause of post-harvest rot in apples. Infected fruits develop dark, circular, sunken lesions with alternating rings of light and dark tissue, which resemble the eye of a bull.

Effective management requires a multi-faceted approach. Key strategies include pruning out and destroying infected branches to reduce inoculum, and painting large pruning cuts to prevent fungal entry. Fungicide applications, particularly copper-based products applied during the dormant season, are crucial. Maintaining tree health through proper fertilization and irrigation helps trees resist infections better.