Field evaluation of conidia of Beauveria bassiana (Balsamo) Vuillemin strain CS-1 against diamondback moth larvae

The efficacy of conidia of Beauveria bassiana (Balsamo) Vuillemin strain CS-1 that showed high mortality in laboratory and net house was examined against diamondback moth larvae in the field. Conidia ( conidia/ml) were applied to larvae on chinese cabbage in a 1.5% emulsifiable oil-emulsion amended with 4% clay at a volume of 0.55 L/3.3 . There were no significant differences among plants and replicates in the deposition of spray droplets on water-sensitive papers or of conidia on leaves and larvae. Weather conditions were rainy and cool during first few days, and then hot and dry. Persistence of conidia was equally short on both leaves and larvae. Nevertheless, treatment of B. bassiana potentially reduced larval populations. But the field efficacy was lower than the laboratory efficacy. This reduced efficacy was ascribed to unfavorable environmental conditions.