Effect of Ozonated Water on Postharvest Pathogens of Pear in Laboratory and Packinghouse Tests. R. A. Spotts, Oregon State University, Mid-Columbia Agricultural Research and Extension Center, Hood River, OR 97031. L. A. Cervantes, Oregon State University, Mid-Columbia Agricultural Research and Extension Center, Hood River, OR 97031. Plant Dis. 76:256-259. Accepted for publication 8 October 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0256.

In treatments with aqueous ozone solutions for 5 min, LD₉₅ values for spores of Botrytis cinerea, Mucor piriformis, and Penicillium expansum were calculated to be 0.99, 0.69, and 0.39 μg of ozone per milliliter of water, respectively. Spore inhibition was directly correlated with ozone concentration in 1- to 5-min exposure times; eight regressions of spore inhibition with concentration were significant at P = 0.01, and one was significant at P = 0.05. However, in pear fruit (Pyrus communis ‘d’Anjou’) wound-inoculated with P. expansum and then treated with water containing up to 5.5 μg of ozone per milliliter for 5 min, levels of decay were similar to those of a control treated with water alone. In a commercial packinghouse test, fewer propagules of Alternaria spp. were recovered from chlorinated water than from ozonated water, whereas equal numbers of propagules of both Cladosporium and Penicillium spp. were recovered. Similar levels of decay were recorded in pear fruit floated through ozonated dump tank water and in fruit treated with chlorinated water, after storage at –1 C for 5 mo.