Abstract:

To identify the toxicity of fluralaner and its joint action with four traditional insecticides (chlorpyrifos, indoxacarb, deltamethrin and emamectin benzoate) to Spodoptera litura F. and explore the optimum ratio of insecticides, the 3rd instar larvae of S. litura and artificial food mixing insecticides were used in the study, the toxicity was measured and the joint action was evaluated by co-toxicity coefficient. The results of single dosage showed that fluralaner, deltamethrin and emamectin benzoate exhibited high activity with LC₅₀ values of 0.48, 0.65 and 0.38 mg/kg at 48 h, respectively. Meanwhile, chlorpyrifos and indoxacarb exhibited moderate activity to S. litura with LC₅₀ values of 8.71 and 3.08 mg/kg, respectively. The results of joint action showed that fluralaner mixing with chlorpyrifos at 3:2, the mixture showed the highest synergistic effect with co-toxicity coefficient (CTC) as 164.2, the mixture with indoxacarb showed additive effect, the mixture with deltamethrin or emamectin benzoate showed antagonistic effect. In conclusion, these results demonstrate that fluralaner and chlorpyrifos could be considered as effective insecticidal mixture to be used for control of S. litura. On the contrary, the fluralaner and deltamethrin or emamectin benzoate should avoid combined application due to their antagonism.

Key words: insecticide, Spodoptera litura F., fluralaner, insecticide mixture, co-toxicity coefficient