Sensitivity of the Entomopathogenic Fungi, Beauveria bassiana, Verticillium lecanii, and Verticillium sp. to Fungicides and Insecticides1

Abstract

Nine fungicides and 14 insecticides and acaracides were tested in vitro on various isolates of the entomopathogenic fungi, Beauveria bassiana , Verticillium lecanii and Verticillium sp. Two techniques were employed: for Verticillium, a “poisoned-bait” method, showing growth inhibition; for B. bassiana , a poisoned-agar disc method, showing inhibition of conidial germination. All chemicals except white summer oil caused some inhibition to Verticillium growth at 10−4 of the recommended dosages for use. Great variations in sensitivity toward a particular fungicide (e.g., captan, copper oxychloride, dinocap, binapacryl) were found among isolates of the same fungal species of both genera, and were also observed with some insecticides (e.g., trichlorfon and narrow-range paraffinic oil on Verticillium ). Among the fungicides, benomyl (methyl 1-[butylcarbamyl]-2-benzimidazole carbamate) and maneb caused the greatest inhibition of all isolates of both genera at recommended dosages and at 10−1 concn, indicating that their use in field or grove would endanger the fungi. At recommended dosages, copper oxychloride and dinocap were the most innocuous to all the fungi (with the exception of 1 isolate of B. bassiana ). Binapacryl had no effect on spore germination of B. bassiana but moderately inhibited growth of most isolates of Verticillium spp. Daconil 2787™ (tetrachloroisophthalo-nitrite) proved moderately fungitoxic to Verticillium and less so to B. bassiana . Among insecticides, sodium fluorosilicate, dichlorvos, and chloropyrifos at recommended dosages were strongly inhibitory to growth of Verticilium spp., but only sodium fluorosilicate inhibited germination of B. bassiana .