Effect of Transgenic Cotton on Arthropod Diversity under Sprayed and Unsprayed Conditions in Cotton Agro-ecosystem

Studies on the diversity of arthropod community in RCH 134 Bt and non-Bt cotton hybrid were carried out under sprayed and unsprayed conditions in the farmer's field at Mansa district of Punjab during 2006. 134 species of arthropods, including 54 species of herbivorous arthropods, 44 species of natural enemies, 26 species of casual visitors and 10 species of pollinators, were found to be associated with the cotton crop. The index of diversity (Shannon Weaver's index) of arthropod communities and sub-communities was higher in sprayed as compared to the unsprayed treatments. Diversity of all sub-communities except Lepidoptera was higher during the reproductive phase of the crop. Lepidopteran sub-community diversity was higher than other sub-communities throughout the season. Higher diversity was due to greater equitability among the arthropod species. The arthropod communities showing lower diversity showed higher dominance of certain species.