Fitness costs associated with chlorantraniliprole and spinetoram resistance in Spodoptera frugiperda (Lepidoptera: Noctuidae) under different temperatures

Fitness cost associated with insecticide resistance and its magnitude can be affected by many environmental aspects, such as temperature. Insect pests can express different phenotypes in response to modified environmental conditions. In this context, we investigated the impact of temperatures: 18, 22, 28, and 32 °C on the magnitude of fitness costs associated with resistance. Different biological parameters were compared between the chlorantraniliprole (Iso-Diam) and spinetoram (Iso-Spin) near-isogenic resistant strains of S. frugiperda and the laboratory-susceptible S. frugiperda strain (Sus). We also assessed the effect of these temperatures on susceptibility to both insecticides through concentration-response curves. Significant differences were observed in the parameters of the fertility life table of the Iso-Diam and Iso-Spin strains compared with the Sus strain at temperatures of 18 and 28 °C. The relative fitness of the Iso-Diam and Iso-Spin strains at temperature of 18 °C was 0.60 and 0.80, respectively. At temperature of 28 °C, the relative fitness of the Iso-Diam strain and the Iso-Spin strain was 0.53 and 0.88, respectively. The resistance ratios of the strains resistant to spinetoram and chlorantraniliprole were higher at temperatures of 18 and 32 °C. These results indicate that fitness cost and susceptibility to chlorantraniliprole and spinetoram in S. frugiperda are affected by different temperatures. Our work can help in the decision-making design process of resistance management programs given the impact of temperature on insect biology and the occurrence of S. frugiperda in regions with different temperatures.