Population build-up of natural enemies in cotton habitat after insecticidal applications at farmer’s field

Abstract

Genetically modified (GM) cotton crop extensively cultivated in tropical and sub-tropical regions worldwide. An experiment was conducted twice in crop season at five different locations to record the relative toxicity and build-up of natural enemies after application of different insecticide at farmers' fields. During the first application of insecticides, emamectin benzoate 50 SG + flonicamid 50 SG (0.42 ladybird beetle, 0.84 green lacewing, 2.11 spiders, 0.29 yellow paper wasp/plant and 4.98% nymphal parasitization of whitefly) favoured to build up more compared to dinotefuran 20 SG + imidacloprid 70 WG treated plots (0.34 ladybird beetle, 0.57 green lacewing, 1.44 spiders, 0.17 yellow wasp per plant and 4.52% whitefly nymph parasitization). In pursuit of second application, average build-up in flonicamid 50 WG + imidacloprid 200 SL i.e., 0.49 ladybird beetle, 0.49 green lacewing, 1.64 spiders, 0.24 yellow paper wasp/plant and 3.93% nymphal parasitization of whiefly observed on lower side, while in flonicamid 50 WG + thiamethoxam 30 FS recorded 0.57 ladybird beetle, 0.73 green lacewing, 1.81 spiders, 0.37 yellow wasp/plant and 4.17% nymphal parasitization exhibited to favour more of numbers of natural enemies. Thus, while selecting an insecticide for the management of a target pest, negative effects on natural enemies, it’s survival and growth, reproduction and changes in behaviour must be kept in mind.