Lambda-cyhalothrin exposure, mating behavior and reproductive output of pyrethroid-susceptible and resistant lady beetles (Eriopis connexa)

Insecticide resistance is a ubiquitous consequence in arthropod pest species subjected to insecticide use in agricultural fields. The widespread use of insecticides also allows selection of insecticide resistance among non-target arthropod species, such as natural enemies. Nonetheless, the potential consequences of sublethal insecticide exposure in resistant natural enemies are frequently neglected. The detected pyrethroid resistance in the lady beetle Eriopis connexa (Germar) in Brazilian agricultural fields afford the opportunity of assessing the consequences of the sublethal exposure of the broadly used pyrethroid insecticide lambda-cyhalothrin in the mating behavior and reproductive output of susceptible and resistant populations of this species. Survival bioassays with lambda-cyhalothrin allowed estimation of sublethal exposure times at the maximum labeled rate to assess the reproductive consequences of such exposure in pyrethroid-susceptible and resistant strains of E. connexa. Such sublethal exposures led to significant difficulties in female mounting by male of both populations. Pyrethroid exposure also extended the duration of female body tremulation and of coupling, while latency to mate, tremulation, coupling and female shaking to dislodge the males after coupling differed between strains with interacting effect of insecticide exposure only for the latter behavior. As a consequence mainly of latency to mate, progeny production was significantly smaller among pyrethroid-resistant females where lambda-cyhalothrin exposure exhibited a negligible effect. Thus, population rather than exposure itself prevailed in determining reproductive output of E. connexa and pyrethroid resistance incurred in reproductive costs in this species that may counterweight the benefits of its survival.