Field trials were conducted during the kharif season of 2016 and 2017 in the farmers’ field of Kalain and Borkhola development block of Cachar district of Assam for evaluation of efficacy of insecticides and bio-pesticides against rice stem borer and leaf folder in the field of High Yielding Variety (HYV) rice, Ranjit. The experiment comprised of 4 treatments including the farmers practice (FP). The study revealed that, lowest mean percentage of infestation of rice stem borer and leaf folder i.e. 3.52 and 2.58 per cent was recorded after 90 days of application with 85.27 and 89.73 per cent reduction over farmers practice in the plots treated with carbafuron 3G @30 kg/ha + 8 release of Trichogramma chelonis 50000/ha/week and Trichogramma japonicum @ 50000/ha/week in the main field + spraying of neem based pesticide @5 ml/litre between 4th and 5th release of T. chelonis and T. japonicum (T1), followed by 7.10 and 4.37 per cent with 70.29 and 80.31 per cent reduction over farmers practice when treated with Chloropyriphos 20 EC @ 2 ml/litre at vegetative and reproductive stage (T2) and 8.0 and 5.17 per cent infestation was recorded when treated with quinalphos 35 EC @ 2.5ml/litre at vegetative and reproductive stage (T3) with 65.29 and 76.70 per cent reduction over farmers practice. In the farmers’ practice highest mean infestation of 23.90 and 22.20 percent was recorded after 90 days of application of furadon 3G @ 7.5 kg/ha (FP). Highest average yields of both the year 46.25 ql/ha was recorded in T1 with an increase of 27.44per cent over farmers’ plot. In T2 average yield of 43.51 ql/ha was recorded with 19.90 per cent increase over FP, followed by 42.45 ql/ha in T3 with an increased percentage of 16.97 over FP. The lowest average yield of 36.29 ql/ha was recorded in FP. Similarly, highest B: C ratio of 1.58 (2016) and 1.579 (2017) was recorded in T1 followed by 1.47 (2016) and 1.51 (2017) in T2 and 1.43 (2016) and 1.47 (2017) was recorded with least B: C ratio of 1.30 (2016) and 1.34 (2017) was recorded in farmers plot (FP).

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