Radio Frequency Treatment to Control Postharvest Brown Rot in Stone Fruit

Brown rot caused by Monilinia spp. is the most important postharvest disease of stone fruit. The growing public concern over the health and environmental hazards associated with high levels of pesticide use have resulted in a significant interest in the development of alternative non-chemical control methods. Radio frequency (RF) treatment at 27.12 MHz was studied to control brown rot in peaches and nectarines. From preliminary studies, a RF treatment for 18 min was selected to evaluate the effectiveness of the treatment to control Monilinia spp. in naturally infected fruit and fruit with different diameters. In general, high disease control was achieved in peaches, however, RF effectiveness was affected by fruit size and no brown rot control was observed in nectarines. In order to address these problems, RF treatment with fruit immersed in water was studied. RF treatment in fruit immersed in water at 20 degrees C for 9 min significantly reduced brown rot incidence in both peaches and nectarines and no significant differences in RF effectiveness were observed depending on fruit size. Moreover, the decrease in treatment time with increasing water temperature was also evaluated. Reduction of treatment time to 6 and 4.5 min was achieved by increasing water temperature at 35 and 40 degrees C, respectively, to control brown rot without impair fruit quality in both, peaches and nectarines. Finally, RF treatment with fruit immersed in water at 40 degrees C for 4.5 min was selected to control Monilinia spp. in naturally infected fruit in which brown rot reduction observed was higher than 74 % in all the varieties evaluated.