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

Abstract

1. 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 2. 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.3. Predator biomass was 66% lower in plots treated with clothianidin compared to controls and this effect persisted across the growing season. 4. 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%.

Neonicotinoid contamination in conservation areas affects bees more sharply than beetles

“…In contrast to bees, beetle abundance, richness, and feeding guild abundances were driven by environmental factors and not clothianidin contamination. These findings are contradictory to previous work indicating a negative impact of clothianidin on arthropod abundance (Main et al, 2018), beetle herbivores (Dembilio et al, 2015;Harmon et al, 2023) and predators (Pisa et al, 2017;Harmon et al, 2023). It is important to note that very few studies examine the effects of neonicotinoids on feeding guilds in restoration habitatsmany being conducted in laboratory settingsand most studies focus on a specific family or species and not the broader community.…”

“…In their 2023 arthropod community-level study, Harmon et al (2023)saw a reduction in arthropod herbivore and predator biomass in response to clothianidin contamination in a prairie restoration. These reductions in herbivore and predator biomass were inconsistent with our findings, but they could be indicative of trends that were not captured in our study.…”