Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2003
Publication Date: 6/20/2003
Citation: Karabulut, A.K., J.L. Smilanick, F. Mlikota-Gabler, M. Mansour, S. Droby. 2003. Near-harvest applications of Metschnikowia fructicola, ethanol, and sodium bicarbonate to control postharvest diseases of grape in central California. Plant Disease, 87(11):1384-1389. Interpretive Summary: Table grapes are attacked by fungi that cause them to rot after harvest. We found applications of ethanol, sodium bicarbonate, or a biological control yeast to fruit on vines before harvest could reduce the rot losses that occurred after harvest during cold storage and simulated marketing periods at warmer temperatures. This research introduces several treatments that can be applied before harvest that can provide some control of postharvest decay, and can reduce the need for postharvest sulfur dioxide fumigation.
Technical Abstract: The yeast Metschnikowia fructicola, ethanol, and sodium bicarbonate (SBC), alone or in combinations, were applied to table grapes on vines 24 h before harvest to control the incidence of postharvest diseases. In four experiments, all signficantly reduced the total number of decayed berries caused by Botrytis cinerea, Alternaria spp., or Aspergillus niger after storage for 30 days at 1C followed by 2 days at 20C. In three epxeriments, a mean gray mold incidence (caused by B. cinerea) of 34.2 infected berries per kilogram among untreated grape was reduced by Metschnikowia fructicola at 2 x 10(7) CFU/ml, ethanol at 50% (vol/vol), or SBC at 2% (wt/vol) to 12.9, 8.1, or 10.6 infected berries per kilogram, respectively. Ethanol, SBC, and SO2 generator pads were similarly effective. M. fructicola effectiveness was not improved when combined with ethanol or SBC treatments. Ethanol and yeast treatments did not harm the appearance of the grapes. M. fructicola and SBC left noticeable residues, an dSBC caused some visible phytotoxicity to the rachis and berries. Ethanol applied at 50% (vol/vol) reduced epiphytic fungal and bacterial populations by about 50% compared with controls. M. fructicola populations persisted on berries during storage when applied alone or after ethanol treatments, whereas SBC reduced its population significantly.