Chapter fourteen - Fitness costs of resistance and their potential application for insect resistance management

Abstract

Fitness costs of insecticide resistance arise, in the absence of insecticide, when individuals that possess alleles for insecticide resistance have lower fitness than insecticide-susceptible individuals. Fitness costs are important for insect resistance management because they can delay the evolution of resistance, and because they can lead to a decrease in the magnitude of resistance when an insecticide is absent. This chapter focuses on the application of fitness costs to manage resistance to conventional insecticides and transgenic insecticidal crops that produce toxins derived from the bacterium Bacillus thuringiensis. For fitness costs to delay the evolution of resistance, it is essential that insecticide-free refuges exist within the agricultural landscape. In some cases, an agricultural landscape may be manipulated to magnify fitness costs, for example, by using an alternative insecticide that imposes negative cross-resistance. The use of integrated pest management, in particular the use of economic thresholds and diversified management approaches, provides a way to increase the prevalence of refuges by reducing insecticide applications, and this, in turn, can increase the delays in resistance imposed by fitness costs.