Joint action toxicity of imidacloprid and pymetrozine on the melon aphid, Aphis gossypii

The cotton and melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a polyphagous pest with a wide host range. The application of chemical insecticides has long been the most common method of controlling this pest. One of the management strategies of insect resistance with pesticides is to use multiple pesticides simultaneously. In this research, imidacloprid and pymetrozine were assessed in the laboratory and greenhouse separately and in mixtures on A. gossypii on greenhouse cucumber. According to the results, mixing these two insecticides in different ratios had different synergistic, additive and antagonistic effects. Among the observed synergistic effects, the best effect was seen with the ratio 1:1 (imidacloprid: pymetrozine). The sublethal effects of applying low lethal concentrations of imidacloprid, pymetrozine and their mixture were evaluated using demographic toxicology based on the age-stage two sex life table methodology. The natural intrinsic rate of increase values (r) for control, imidacloprid, pymetrozine and ratio 1:4 (imidacloprid: pymetrozine) exposed populations were 0.39, 0.22, 0.31 and 0.23 day(-1), respectively. Our findings revealed that an effective control of A. gossypii will be achieved with lethal and low lethal concentrations of the mixture of the two insecticides in greenhouse and laboratory conditions.