Apple ring rot

Apple ring rot is a serious fungal disease caused by the pathogen Botryosphaeria kuwatsukai. It is a widespread condition affecting pome fruit trees, leading to both branch dieback and significant post-harvest losses in fruits due to decay.

The disease primarily impacts apple and pear trees, though it can occasionally affect other hosts. The fungus attacks the vascular and cortical tissues of the branches, as well as the fruit skin, causing rapid development of necrotic lesions during the growing season.

The most distinctive symptom is the appearance of ring-like brown, sunken spots on the fruit, which often result in complete decay of the flesh. On the branches, the fungus causes localized bark necrosis, cracking, and cankers that eventually girdle the branches, leading to the death of distal growth.

The development of the fungus is favored by warm, humid weather conditions. Inoculum spreads via wind-borne spores and water splashes during rainfall. The pathogen overwinters within infected bark tissues and mummified fruits remaining in the canopy or on the ground, serving as a source for primary infection the following spring.

Effective management strategies require a combination of cultural and chemical practices. Maintaining tree vigor, removing and destroying infected branches and mummified fruit, and applying registered fungicides during high-risk periods are essential to reduce inoculum levels and protect healthy tree tissues from colonization.