CONTROL OF POSTHARVEST BROWN-ROT OF NECTARINES AND PEACHES BY PSEUDOMONAS SPECIES

Microbes were applied to nectarines and peaches to control postharvest brown rot caused by Monilinia fructicola. Two yeasts applied to wound s on fruit before inoculation protected fruit from subsequent infectio n, but they could not control decay when applied after inoculation. Tw o antibiotic-producing bacteria, Pseudomonas corrugata and P. cepacia, significantly reduced decay when applied up to 12 h after inoculation . P. corrugata controlled decay with fewer colony-forming units (c.f.u .) than P. cepacia; <10(4) c.f.u. per wound of P. corrugata controlled decay, whereas P. cepacia required greater-than-or-equal-to 10(5) c.f .u. per wound. Both antagonists grew rapidly in wounds but not on the intact surface of fruit. Washed cells controlled decay but filter-ster ilized culture fluids did not. Both bacteria controlled the decay of w ound-inoculated peaches better than thiabendazole, and P. corrugata wa s only slightly inferior to triforine. In tests employing very high in oculum densities of M. fructicola, both pseudomonads significantly red uced decay but were inferior to isolate B-3 of Bacillus subtilis. Deca y was poorly controlled by the pseudomonads in tests with commercial f ruit that was not artificially inoculated. Infections characteristic o f commercially grown fruit were not accurately simulated by the artifi cial inoculation methods used to select antagonists. Revised strategie s to control brown rot by microbial antagonists are discussed.