Chlorine and Chlorine Dioxide for Control of d’ Anjou Pear Decay. R. A. Spotts, Assistant Professor, Department of Botany and Plant Pathology, Oregon State University, Mid-Columbia Experiment Station, Hood River 97031. B. B. Peters, Experimental Biology Technician, Oregon State University, Mid-Columbia Experiment Station, Hood River 97031. Plant Dis. 64:1095-1097. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-1095.

The effects of chlorine and chlorine dioxide on germination of Botrytis cinerea, Mucor piriformis, and Penicillium expansum and on d’Anjou pear decay were studied under laboratory and commercial packinghouse conditions. Chlorine at 50 µg/ml significantly reduced conidial germination of all decay fungi after 0.5-min treatment and at 2.5 and 5.0 µg/ml reduced M. piriformis and P. expansum germination after 5 min. A 0.5-min treatment with chlorine dioxide at 10 µg/ml significantly reduced germination of all decay fungi but did not affect conidial germination at 0.1, 0.5, and 1.0 µg/ml. Treatment with chlorine (50 µg/ml) or chlorine dioxide (10 µg/ml) significantly reduced fruit decay, but decay was not controlled when conidia were treated with chlorine dioxide at 0.1, 0.5, or 1.0 µg/ml or chlorine at 0.5, 2.5, or 5.0 µg/ml. Immersion of inoculated fruits in chlorine or chlorine dioxide in commercial packinghouse flumes did not reduce decay. Use of chlorine dioxide for control of pear fruit decay does not presently appear economically feasible.

Keyword(s): Pyrus.