Comparative effectiveness of deltamethrin, imidacloprid and emamectin benzoate alone and in binary blends to control Trogoderma granarium: Effect on macronutrients

Trogoderma granarium Everts (Insecta, Dermestidae) severely attacks a variety of stored commodities, and its control has been achieved by conventional insecticides. However, unplanned use of insecticides leads towards emergence of resistance as well as health and environment damage. Previous studies reported insecticidal efficacy of deltamethrin (DL), emamectin benzoate (EB) and imidacloprid (IM) individually but lacking efficacy of mixtures against T. granarium. The study presented here was aimed at investigating the susceptibility of field collected Mandi Bahaud Din (MBD) population (14 years DL exposure history) and a DL susceptible LAB-S population (not exposed to insecticides since 2001) against DL, EB and IM individually and in binary mixtures (DL:EB, DL:IM and EB:IM) at different ratio (1:1, 1:2, 1:3, 2:1 and 3:1). The MBD strain showed greater susceptibility against IM and EB (LC50 473.09 and 556.4 ppm) respectively, but decreased susceptibility (LC50 808.67 ppm) against DL indicating DL resistance. The LC50 values were 251.62, 307.15 and 369.73 ppm against DL, IM and EB, respectively in LAB-S strain. All binary mixtures exhibited synergistic interactions against MBD strain and EB:IM mixture (3:1) was found the most effective (RTU 3.93) among all the tested combinations. In contrast, EB:IM mixture showed antagonistic interactions (1:1, 1:2, 1:3, 2:1) but synergistic interactions were achieved by increasing EB concentration (3:1, RTU 1.23) in mixture against LAB-S strain. However, DL:EB was more effective (RTU 2.1) against LAB-S strain among all the tested combinations. The toxic effect of LC20 of most effective mixture on macronutrients was also investigated. A significant reduction in contents of trehalose, total protein, soluble protein, total lipids and glycogen while an increase in glucose and free amino acids was observed in both strains in comparison with their respective unexposed control. It is concluded that binary mixture reduces the net quantity of conventional insecticides, thus offering more effective approach to control T. granarium.