Abstract

A blended pesticide, 25% pymetrozine-thiamethoxam suspension concentrate (SC), was evaluated for its insecticidal activity against rice planthoppers in a greenhouse and field. The results of the seedling-dipping and rice-stem-dipping methods used in the greenhouse indicated the excellent activity of the SC against the brown rice planthoppers, with the lethal concentration causing 50% mortality (LC₅₀) values reaching 3.27 and 3.79 μg/ml, respectively. The co-toxicity coefficient (CTC) value >120 indicated that the obtained SC had a synergistic effect. The results from the field efficacy trials revealed that the controlling effect of the proposed reagent on rice planthoppers was better than (or comparable with) commercial insecticide-25% pymetrozine SC and 2.2% abamectin-imidacloprid emulsifiable concentrate (EC) at comparable doses and differential time intervals. The proposed reagent had low toxicity from the data of acute oral, acute dermal, eye irritation and skin irritation. These characteristics suggested 25% pymetrozine-thiamethoxam SC as a potential candidate insecticide.

Key words: 25% pymetrozine-thiamethoxam suspension concentrate, rice plant hopper, toxicological test, field efficacy.