Biological control of postharvest diseases of peach with phyllosphere isolates of Pseudomonas syringae

Commercially ripe peaches were wounded and co-inoculated with phylloplane i solates of Pseudomonas syringae (MA-4 and NSA-6), Pseudomonas fluorescens ( BAP-3), or an isolate of Candida sp. (NSD-4) in combination with either con idia of Monilinia fructicola (cause of brown rot) or sporangiospores of Rhi zopus stolonifer (cause of rhizopus rot). Isolates NSA-6 and MA-4 at a conc entration of 1 x 10(7) CFU/mL reduced brown rot to 28% and 73%, respectivel y, from 98% in the inoculated check after 5 days incubation at 22 degrees C . Both isolates reduced rhizopus rot to 5% and 8% from 53% in the inoculate d check after 5 days incubation. The P. syringae isolates when used in 2-mi n soak treatments were less effective against natural, preharvest M. fructi cola infections of late-harvested peaches. Isolates MA-4 and NSA-6 suppress ed brown rot from 63% to 30% and from 95% to 71-81%, respectively, after 3 and 4 days incubation at 22 degrees C. The use of 0.5% CaCl2 in the soak su spension significantly improved the activity of P. syringae but the use of "peach wax" (Decco 282) increased brown rot incidence and negated the benef icial effect of CaCl2.