Bactericidal Treatment for the Eradication of Erwinia amylovora from the Surface of Mature Apple Fruit. W. J. Janisiewicz, Research Plant Pathologists, USDA-ARS, Appalachian Fruit Research Station, Kearneysville, WV 25430. T. Van Der Zwet, Research Plant Pathologists, USDA-ARS, Appalachian Fruit Research Station, Kearneysville, WV 25430. Plant Dis. 72:715-718. Accepted for publication 21 March 1988. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1988. DOI: 10.1094/PD-72-0715.

Several chemicals were evaluated for their effectiveness in eradicating viable Erwinia amylovora cells from aqueous suspensions and from the surfaces of artificially infested apple fruit. In vitro, 12 mg/L of sodium hypochlorite (NaOCl) and 62 mg/L of benzalkonium chloride (BC) eliminated all viable bacteria. Time of exposure to the bactericides had a significant effect on survival of E. amylovora. Addition of Ortho X-77 surfactant to the bactericides reduced the efficacy of the NaOCl solution, but had no apparent effect on BC. On artificially infested apple fruits, NaOCl at 450 and 500 mg/L plus 0.25% of surfactant greatly reduced, but did not totally eliminate, viable bacteria. All bacteria were eradicated from the apple surface with 1,400 mg/L of BC plus 0.5% surfactant. The eradicative effect was confirmed by passing buffer washings of treated fruit through millipore (0.2 ?m) membrane filters that were subsequently incubated on selective media for possible development of E. amylovora colonies. Dip treatment with BC offers a possible remedy for meeting quarantine requirements for shipment of pome fruits to countries free of fire blight.

Keyword(s): Malus.