Effect of surfactant on the efficacy of insecticides against onion thrips (Thrips tabaci)

The present experiment was carried out with an objective to find out the effect of surfactant on the efficacy of insecticides, because the use of insecticides for the control of onion thrips (Thrips tabaci Lindeman) is relatively less promising due to onion leaf pattern and texture. The minimum thrips population (6.48/plant) and thrips incidence (19.57%) were recorded at 15 days after spray in the fipronil 5 SC at 2 ml + surfactant at 0.5 ml/l of water, followed by lambda cyhalothrin 5 EC at 2 ml + surfactant at 0.5 ml (8.85/plant and 21.51%, respectively). While, imidacloprid 17.8 SL alone at 0.4 ml/l of water showed higher thrips population (21.78/plant) when compared to other treatments and which was found at par with untreated control. The efficacy of insecticides was significantly increased by addition of surfactant from 14.60 to 33.20 and 7.52 to 23.10% in minimizing the number of thrips/plant and thrips incidence %, respectively. The minimum thrips damage severity (1.36) and maximum bulb yield (254.83 q/h) with highest cost benefit ratio (1:6.84) was recorded in fipronil 5 SC at 2 ml + surfactant at 0.5 ml/l of water followed by lambda cyhalothrin 5 EC at 2 ml + surfactant at 0.5 ml (1.62, 249.50 q/ha and 1:6.14, respectively). Fipronil 5 SC and lambda cyhalothrin 5 EC without surfactant showed intermediate thrips damage severity (1.68 and 1.96, respectively), bulb yield (241.53 and 238.52 q/ha, respectively), and cost benefit ratio (1:5.68 and 1:5.26, respectively). The insecticides along with surfactant reduced the thrips damage severity (10.46–19.05%) and increased the bulb yield (1.97–5.51%) in different treatments when compared with the insecticides without surfactant. Along with insecticides the use of surfactant could be highly desirable.