Chestnut sclerotinia

The fungus Sclerotinia echinophila is a specialized pathogen responsible for the development of fruit rot in the sweet chestnut (Castanea sativa). As an ascomycete fungus, it primarily affects the nuts, causing severe losses during the late stages of development and throughout the storage period.

The host range is essentially limited to chestnut species. The pathogen typically enters the developing nuts through natural openings or physical injuries. Infestations are significantly exacerbated by the presence of chestnut weevils, which provide an entry point for the mycelium to colonize the fruit interior.

Symptoms initially appear as dark, necrotizing spots on the spiky burr and the shell of the nut. As the infection progresses, the internal kernel becomes discolored and shrinks as it is consumed by the fungal hyphae. Eventually, the fungus produces hardened, black structures known as sclerotia, which serve as the primary overwintering units.

Development and spread of Sclerotinia echinophila are driven by environmental conditions. Mild, humid autumns are particularly favorable for the germination of sclerotia stored in the soil. Once active, the fungus releases spores that are wind-dispersed, leading to secondary infections across the orchard canopy.

Effective management strategies focus on sanitation and orchard hygiene. Growers should prioritize the collection and destruction of fallen fruit and debris where the fungus survives during the winter. Integrated pest management, particularly targeting nut-boring insects, is essential to minimize the infection rate. Proper post-harvest handling, such as rapid drying and cool storage, remains the standard for maintaining nut quality.