Comparative efficacy, non-Target toxicity and economics of seven novel pre-mixed formulations against Maruca testulalis G. and Aphis craccivora K. infesting cowpea

Abstract

Aim: Cowpea is one of the most important legume vegetables commercially cultivated crop in India and is severely prone to attack by both chewing and sucking insect pests. As the most effective tool of IPM, proper selection of ready-mix insecticides is required for eco-friendly and simultaneous management of these insect pests to reduce the cost of protection. The main objective of the study was to evaluate the relative field-effectiveness vis.-A-vis. non-Target toxicity and economics of seven new generation pre-mixed formulations against spotted pod borer {Maruca testulalis G.) and bean aphid {Aphis craccivora K.) infesting cowpea. Methodology: Two rounds of insecticides spraying were done at40-50% flowering stage, followed by next at 15 days interval. The numberof target pests was counted 24 hrs before first spray followed by 3,7,10 and 14 days after first and second spray, respectively. Data of pod infestation was recorded 10 days after each spray and at harvest. Percent reduction or increase (+) of Chrysoperla sp. and Micraspis discolorwas also worked out at 15days aftereach spray. Mean yield of green pods were recorded and converted intoquintals perhectare. Results: Chlorantraniliprole+thiamethoxamshowed maximum impact (60.68%) than emamectin benzoate +fipronil (60.66%) and flubendiamide + thiacloprid (60.35%) considering the mean percent reduction of pod damage caused by pod borer, while later proved most superior among all the test combinations in percent reduction of M.Testulalis larval population with higher persistency. Highest aphid mortality was recorded in pyriproxyfen + fenpropathrin (80.71% and 80.90%) and fipronil + imidacloprid (79.24% and 79.54%) treated plots after first and second spray, respectively, during both the years. Chlorantraniliprole + thiamethoxam and flubendiamide + thiacloprid proved least toxic to the prevailing predatory fauna Micraspis discolor (Fabricius) and Chrysoperla sp., with less than 10% mortality after 15 days of each insecticide imposition. Highest green pod and seed yield was also recorded from flubendiamide+thiacloprid (13.78 and 1.91 q ha1) treated plots and highest cost: benefit ratio (1:6.8) was obtained from both the combinations of flubendiamide + thiacloprid and emamectin benzoate+fipronil. Interpretation: The outcome of this study experiment will encourage the farming community in selecting new generation pre-mixed insecticides like flubendiamide 24%+thiacloprid 24% SC or chlorantraniliprole 10%+thiamethoxam 20% SC or emamectin benzoate 5%+fipronil 15% WDG, those might sustain toxicity against spotted pod borer and bean aphid for a longer period with least possibility of resistance development.