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Prevention of Ascocarp Formation in Claviceps purpurea by Fungicides Applied over Sclerotia at the Soil Surface. John R. Hardison, Research Plant Pathologist, Plant Science Research Division, ARS, USDA, and Department of Botany and Plant Pathology, Oregon Agricultural Experiment Station, Corvallis 97331; Phytopathology 62:609-611. Accepted for publication 6 January 1972. DOI: 10.1094/Phyto-62-609.

Twenty-seven systemic and nine protectant fungicides were evaluated for suppression of ascocarp formation in Claviceps purpurea. The chemicals were applied once over sclerotia from Lolium perenne at the soil surface. In one or two separate tests, complete or nearly complete suppression of ascocarps was obtained by application to 92 cm2 of soil surface of benomyl at 1 to 4 mg, triarimol at 0.5 to 2 mg, cadmium chloride at 1 mg, 1,2-bis(3-methoxycarbonyl-2-thioureido)benzene at 2 and 4 mg, and parinol at 2 and 4 mg. These dosages failed to suppress ascocarps in a third test with sclerotia with greater capacity for ascocarp production. Phenyl-5, 6-dichloro-2-trifluoro-methyl-1-benzimidazole-carboxylate (Lovozal) consistently suppressed ascocarp development in all tests at 2 mg/92 cm2 of soil surface, and thus showed the strongest activity of the organic chemicals evaluated. Cadmium chloride may provide an economic chemical control if acceptable for registration.

Additional keywords: ergot control.