Immersion of fruit in water to improve radio frequency treatment to control brown rot in stone fruit

Brown rot caused by Monilinia spp. is the most important postharvest disease of stone fruit. Currently, no chemical fungicides are allowed in the European Union to be applied to stone fruit after harvest, which has increased the need to develop alternative methods. Radio frequency (RF) treatment at 27.12 MHz with fruit immersed in water was studied to control brown rot in peaches and nectarines artificially inoculated with M. fructicola. Additionally, RF treatment in air was also investigated to evaluate the benefit of water immersion to reduce the effect of fruit size on treatment efficacy. RF treatment with fruit immersed in water at 20 °C applied for 9 min significantly reduced brown rot incidence in both peaches and nectarines and no significant differences in RF efficacy were observed depending on fruit size. However, when RF treatment was applied in air for 18 min, brown rot reduction was significantly higher in large fruit than in small fruit. Finally, the decrease in exposure time of radio frequency treatment with fruit immersed in water with increasing water temperature was also studied. Reduction of treatment time to 6 and 4.5 min was achieved by increasing water temperature at 35 and 40 °C, respectively, to control brown rot without adverse external and internal damage in both ‘Baby Gold 9’ peaches and ‘Autumn Free’ nectarines.

Authors are gratefulto the University of Lleida for their financial support by an organic production research project and to Spanish Government for their financial support by a national project AGL2011-30472-C02-01 from Ministry of Science and Innovation and for the grant AP2008-01223 from Ministry of Education. Authors also are grateful to Maria Helena Borralho and Marta Baret for their technical support.