Fitness Costs of Resistance to Bacillus thuringiensis in Colorado Potato Beetle (Coleoptera: Chrysomelidae)

Abstract

We compared fitness components of a Bacillus thuringiensis CryIIIA δ-endotoxin resistant and susceptible strains of Colorado potato beetle, Leptinotarsa decemlineata (Say). The resistant strain had been selected for 35 generations, and the resistance ratio was >700-fold compared with the susceptible strain. The F36 of both strains was used in this study. We found that the viability of eggs produced by resistant and susceptible females were high (97.8 ± 3.7 and 98.3 ± 2.9%, respectively), but eggs of the resistant strain tended to have longer viability than that of the susceptible strain (5.7 ± 0.3 and 5.2 ± 0.2 d, respectively). Slower larval development was associated with resistance to CryIIIA δ-endotoxin in Colorado potato beetle. In addition, resistant females produced 60% fewer eggs than susceptible females. The resistant females also exhibited a shorter oviposition period and fewer eggs per egg mass (16.3 ± 2.4 versus 27.8 ± 11.3). These results are discussed together with various resistance management strategies for Colorado potato beetle controlled by conventional B. thuringiensis sprays and transgenic plants.