Toxicity of the Surfactant Nacconol to Four Decay-Causing Fungi of Fresh-Market Tomatoes. M. W. Hoy, Postgraduate Research Plant Pathologist, University of California, Davis 95616. J. M. Ogawa, Professor, University of California, Davis 95616. Plant Dis. 68:699-703. Accepted for publication 17 February 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-699.

The anionic surfactant Nacconol 90F (active ingredient sodium dodecylbenzene sulfonate) was fungistatic in vitro to mycelia and spores of four decay-causing fungi of California tomato fruit. ED₅₀ values for Botrytis cinerea, Geotrichum candidum, Phytophthora parasitica, and Rhizopus stolonifer were 23, 20, 75, and 27 μg a.i./ml for mycelial growth and 116, 60, 60, and 136 μg a.i./ml for spore germination, respectively. Nacconol was fungicidal to B. cinerea spores at concentrations greater than 5,000 μg a.i./ml. In laboratory tests, B. cinerea decay of injured fresh-market tomatoes was significantly reduced by treating the fruit in Nacconol solutions of 200, 2,000, or 5,000 μg a.i./ml for 3 min at 38 C followed by a fresh-water rinse. However, Nacconol amendments of 200, 2,000, or 5,000 μg/ml did not enhance the ability of 100- or 400-μg/ml chlorine solutions to reduce the incidence of B. cinerea decay. When the water rinse was omitted, Nacconol amendments significantly improved the efficacy of 100-μg/ml but not 400-μg/ml chlorine treatments. Phytotoxicity symptoms developed when fruit were not rinsed after treatment with 2,000 or 5,000 μg/ml Nacconol alone or in combination with chlorine.

Keyword(s): postharvest decays.