Field Efficacy of Certain New Insecticides against Major Insect Pests of Rice at Manipur

Field experiment conducted during kharif, 2012 and 2013 at the Rice Research Farm of the College of Agriculture, Central Agricultural University, Imphal evaluated the efficacy of certain new insecticides against the rice pests viz., Asian gall fly (Orseolia oryzae Wood-Mason), yellow stem borer (Scirpophaga incertulas Walker), leaf folder (Cnaphalocrocis medinalis Guenee) and whorl maggot (Hydrellia philippina Ferino). Against the gall fly, thiamethoxam 25 WG @ 25 g a.i. ha1 was found effective. This was followed by imidacloprid 70 WG @ 50 g a.i. ha−1(4.40% SS) and acephate 50 + imidacloprid 1.8% (Lancergold) 51.8 SP @ 500 g a.i. ha−1 but insignificantly. Flubendiamide 39.35 SC @ 24 g a.i. ha−1 was also found effective against the leaf folder and yellow stem borer with the least leaf damage (LD), dead heart (DH) and white ear head (WEH). It was followed by chlorantraniliprole 18.35 SC @ 30 g a.i.ha−1 and thiamethoxam 25 WG @ 25 g a.i. ha−1 which showed insignificant difference. Against the whorl maggot, thiamethoxam 25 WG @ 25 g a.i. ha−1 was found the best, closely followed by acephate 50% + imidacloprid 1.8%. Maximum grain yield (5.00 t ha−1) was obtained from the plots treated with flubendiamide 39.35 SC, and it was found insignificantly differing from thiamethoxam 25 WG (5.00 t ha−1), at par with acephate 50% + imidacloprid 1.8% 51.8SP (4.83 t ha−1), fipronil 5 SC (4.72 t ha−1) and flubendiamide 39.35 SC (4.68 t ha−1). Thiocloprid 21.7 SC gave the least grain yield. The net profit varied from Rs 2353 (thiacloprid 21.7 SC) to Rs. 17288 (thiamethoxam 25 WG) with the cost: benefit ratios ranging from 1: 0.45 to 1: 10.79, the minimum and maximum being with thiacloprid 21.7 SC and thiamethoxam 25 WG, respectively.