Timing of apple fruit infection by neofabraea perennans and neofabraea kienholzii in relation to bull’s-eye rot development in stored apple fruit

Abstract

Bull’s-eye rot is a postharvest disease of pome fruit in the U.S. Pacific Northwest. The disease is caused by the fungi Neofabraea kienholzii, N. malicorticis, N. perennans, and N. vagabunda. Fruit infection by these pathogens is initiated in the orchard during the fruit-growing season but remains latent at harvest. For fruit held in postharvest cold storage, bull’s-eye rot symptom development is slow to progress, requiring at least 3 months before symptoms are first visible. In order to determine the timing of preharvest fruit infection in relation to bull’s-eye rot development in cold storage, ‘Red Delicious’ and ‘Fuji’ apple fruit were inoculated with a conidial suspension of N. perennans or N. kienholzii at different inoculation timings throughout the fruit growing seasons of 2012 to 2014. Fruit were harvested and stored at 0°C for up to 10 months, during which time disease incidence was recorded periodically. Results from this study demonstrate that apple fruit infection by either pathogen may occur at any point during the growing season. However, infections occurring over the 8-week period immediately prior to harvest yield a higher incidence of bull’s-eye rot in stored fruit compared with infections initiated earlier in the growing season.