Changes in predator biomass may mask the negative effects of neonicotinoids on primary consumers in field settings

Abstract

The non-target effects of pesticides, particularly those that are long-lasting and move easily through the environment, could have community-level impacts on beneficial arthropods and hinder conservation efforts in agrolandscapes We assessed the impacts of a neonicotinoid insecticide, clothianidin, and possible synergisms with a fungicide by quantifying predator, herbivore, and pollinator biomass and morphospecies richness in simulated prairie restorations. Predator biomass was 66% lower in plots treated with clothianidin compared to controls and this effect persisted across the growing season. Herbivore biomass was 51% lower in clothianidin-treated plots in June, but the effect waned over the growing season, and no difference was detected in July or August. There was a synergistic effect of clothianidin and fungicide in lowering herbivore morphospecies richness by 12%. Pollinators appeared unaffected by clothianidin. Instead, pollinator biomass increased by 71% with added fungicide in the absence of clothianidin. The results of this study underscore the complexity of pesticide effects in field settings. Additional studies are necessary to understand how pesticide dissipation and predator release may interactively affect late-season herbivore populations.