Abundance and diversity of arthropods in transgenic Bt and non-Bt cotton fields under Indian conditions.

Two-year field studies during Kharif 2015 and 2016 were conducted to assess the abundance and diversity of arthropod communities of Bt cotton carrying Cry1Ac and Cry2Ab proteins and non-Bt cotton under sprayed and unsprayed conditions. The experiment was conducted in a randomized block design with four treatments of BG-II and non-Bt cotton. The treatments were non- transgenic cotton with no insecticide treatment, non-transgenic cotton with insecticide treatment, transgenic cotton with no insecticide treatment and transgenic cotton with an insecticide treatment. Arthropod community categorized as target insect pests, sucking insect pests, natural enemies and non-target insects were recorded at different phases of the cotton crop. The sucking insect pests contributed the highest abundance among the total arthropods recorded during the period of study. The abundance and diversity of bollworms that were recorded from non-Bt cotton only suggested effectiveness of BG II cotton against target insect pests. The abundance, species richness and diversity indices with respect to populations of beneficial predaceous arthropods and non-target insects were similar in BG-II and its non-Bt counterpart under unsprayed conditions. On the contrary, these parameters were significantly on the lower side under sprayed regimes for both genotypes. The spray of insecticides in early season against sucking insect pests significantly reduced their abundance and diversity indices in both BGII and non-Bt cotton. As monocropping of BG-II cotton is common on large parts of India, there is a need to monitor the populations of non-target insect species with special emphasis on sucking insect pests on a continuous basis to understand the long-term impact of Bt crops on insect biodiversity for sustainable integrated pest management practices. [ABSTRACT FROM AUTHOR]