Effect of some pesticides with different target sites on the pink bollworm, Pectinophora gossypiella (Saunders)

Abstract

Laboratory bioassay showed that the conventional pesticide, lambda-cyhalothrin, was more effective than thiamethoxam and buprofezin when tested against the newly hatched larvae of the pink bollworm, Pectinophora gossypiella (Saunders). The LC50 of thiamethoxam, buprofezin and lambda-cyhalothrin was 5.9, 87.5 and 4.9 ppm, respectively. When the synergism agent, piperonyl butoxide (PBO), was combined with the tested pesticides, the toxicity of all pesticides was increased and the LC50 was decreased to 1.4, 15.1 and 2.6, respectively. Some biological aspects (larval duration, pupal stage, number of eggs laid per female and percent of hatchability) were affected by buprofezin treatment more than thiamethoxam and lambda-cyhalothrin. A field experiment showed that lambda-cyhalothrin was the most effective when compared to thiamethoxam and buprofezin. The percentage of reduction in pink bollworm infestation to cotton bolls by using lambda-cyhalothrin, thiamethoxam and buprofezin was 85.7, 39.3 and 19.5%, respectively, during 2009 cotton season, and 80.1, 64.7 and 39.1%, respectively, during 2010 cotton season. These results suggested that lambda-cyhalothrin is the most effective pesticide against the pink bollworm larvae. And also, buprofezin has a good role in incidence of disturbance in developmental process. In addition, the use of synergistic agent PBO has a good role in increasing toxicity of all the tested pesticides especially with thiamethoxam.