Sublethal effects and costs of resistance to abamectin in diamondback moth (Plutella xylostella) (Lepidoptera: Plutellidae)

It is essential to understand the effects of sublethal concentrations of insecticides have on the dynamics, biology, and development of pests such as Plutella xylostella, one of the most important pests in the world. This species can develop resistance to the insecticides used for its control. In the present study, abamectin selection pressure was performed for ten generations of P. xylostella, and the sublethal concentrations (CL20) and susceptible lines of the resistance were determined. Then, these concentrations were applied to third instar larvae. In two generations it was evaluated the effect on the percentage of pupae formed, pupal weight, adult emergence, and the development times of each phase from egg to adult. The resistance and application of sublethal concentrations have considerable costs in the biology and development of P. xylostella by increasing the percentage of pupation from one generation to another, and a greater weight of pupae and eggs per female/day. However, it presents a transgenerational effect by reducing oviposition in its generation; in terms of development time, it presented a harmful effect by prolonging it by more than seven days, which would generate a greater number of applications per cycle.