Effects of Postharvest Chlorine and Wax Treatments on Surface Microflora of Lime Fruit in Relation to Citrus Bacteriosis Disease. J. J. Stapleton, USDA, ARS, Apartado Postal 121, Tecoman, Colima, Mexico. Plant Dis. 70:1046-1048. Accepted for publication 7 July 1986. 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, 1986. DOI: 10.1094/PD-70-1046.

Citrus bacteriosis (CB), a suspected form of citrus canker (Xanthomonas campestris pv. citri[X. c. pv. citri]), is expressed as lesions on leaves and twigs of Mexican lime (Citrus aurantifolia) as well as on other citrus plants in Colima, Mexico. Immersion of Mexican and Persian lime fruit in 200 ppm Cl, as sodium hypochlorite (NaOCl), for 2 min is a prerequisite for movement of fruit out of CB quarantine areas even though no bacteriosis symptoms have been observed on fruit. In addition, most Mexican citrus packers spray fruit with a protective wax coating before shipping. The effects of these treatments on lime surface microflora were evaluated. Total bacteria were reduced by 82–99+%, and fungi, by 81–100% in assays of fruit washings from limes treated with 50–900 ppm Cl as NaOCl. Nevertheless, total bacterial populations of 2.7 × 10²–2.9 × 10³ cfu/cm² of fruit surface survived Cl concentrations above the mandated 200-ppm level. No naturally occurring Xanthomonas spp. were recovered from fruit washings, although bacteria artificially inoculated in high concentrations were recovered at least 2 wk later on lime surfaces. Presumptive X. c. pv. citri was not eradicated when intact or wounded fruit were artificially inoculated with high concentrations of cells, then immersed in 200 ppm Cl for 2 min. The protective wax used in Colima did not increase the efficacy of Cl treatment.