author(s)
A Kuzhandhaivel Pillai, M Ganesh Kumar, S Kuttalam, K Gunasekaran and SV Krishnamurthy

abstract
A field experiment was conducted to assess the impact of emamectin benzoate 5% SG on arthropod diversity in bhendi during March-May, 2014 in Coimbatore. Two rounds of a spray of emamectin benzoate 5% SG were given at fourteen days interval starting from 38 days after sowing (DAS). In other hand an unsprayed field was maintained. The sampling of arthropods were made using four different methods viz., active searching, net sweeping, pitfall trap and rubbish trap. The collected arthropods were sorted out, identified to the lowest possible taxon and the biodiversity indices were estimated. A total of 4093 individuals belonging to 63 species, 43 families and 11 orders in both sprayed and unsprayed okra field were collected. The unsprayed okra field recorded a total of 2388 individuals, whereas sprayed field recorded a total of 1705 individuals. The class Insecta (51 species) was the most dominant followed by Arachnida (12 species). In Insecta, exopterygota were represented by four orders and endopterygota were represented by five orders. Spiders belonging to eleven species, nine genera and six families were recorded. The family Lycosidae (104 individuals) was found to be dominant followed by Salticidae (85 individuals). Family Lycosidae was represented by two species viz., Lycosa sp. and Pardosa birmanica Simon. The biodiversity indices were worked out, and the alpha diversity indices viz., Species richness indices (Species number, Fishers’ alpha index and Shannon-Weiner index), species dominance index (Simpson’s index) and evenness index revealed that maximum value were recorded in unsprayed fields than sprayed fields especially at the time of spraying and the population increased two weeks after the spray. The comparison of beta diversity in sprayed and unsprayed fields, indicated that, based on ordinal, familial, generic and species level, all the indices values were higher in sprayed field than the unsprayed field. Higher arthropod diversity recorded in unsprayed field than the sprayed field.