Core rot is a major postharvest disease of apple fruit that occurs worldwide and is caused by a complex of fungi. Despite the importance of the disease, little is known about its etiology in Greece. In this study, 325 fungal isolates obtained from fruit with core rot symptoms were identified to the species level using morphological characteristics and phylogenetic analysis. Fungal identification revealed that Alternaria alternata was the major disease agent (57.8% of the isolates), followed by Kalmusia variispora (27.8%), Botrytis cinerea (12%), and Fusarium spp. (3.3%). K. variispora is reported for the first time as an agent of core rot of apple and its pathogenicity was confirmed by artificial inoculation tests. In addition to disease etiology, field experiments were performed at two different orchards for 3 consecutive years (2017 to 2019). Experiments were conducted to determine the effectiveness of several classes of fungicides and the timing of application for control of the disease. Greater efficacy was achieved when fungicides were applied at the petal fall stage (flowers fading BBCH 67), while the most effective fungicides were the succinate dehydrogenase inhibitors fluxapyroxad, fluopyram, adepidyn, and penthiopyrad. The results of this study are expected to contribute to the optimization of disease management and reduce the yield losses caused by core rot pathogens in Greece.
Keywords: Alternaria alternata; Kalmusia variispora; adepidyn; fluopyram; fluxapyroxad; moldy core rot; penthiopyrad.