Honey bee workers reared in a neonicotinoid contaminated in-hive environment

ABSTRACTWith the currently updated risk assessment of three neonicotinoid pesticides, the European Food Safety Authority has confirmed that different applications of these substances represent a risk to wild and managed bees and their use was therefore severely restricted. However, to close further gaps in knowledge, this experiment covers exposure of honey bee worker brood reared in a neonicotinoid contaminated in-hive environment with focus on the individual. In a worst case scenario, mini-hives were fed chronically with a sublethal concentration of clothianidin (15 µg/kg), which is highly toxic to bees already in small amounts. Freshly hatched workers from these colonies were subsequently marked and introduced into non-contaminated colonies, where their lifespan and behavior was monitored. Nineteen days after exposure, clothianidin treated bees had no reduced lifespan or showed any signs of behavioral impairment when compared to the control, demonstrating that social buffering is not a simple substitution of dead bees by rearing more brood. Our results suggest that the social environment plays a crucial role for the individual in terms of “superorganism resilience”. These findings are discussed in context with the current use of lower tier test systems in risk assessment and contrary results obtained from laboratory experiments.HIGHLIGHTSSublethal clothianidin treatment did not affect lifespan nor behavior of workers.Effects on individual bees reared within a mini-hive are translatable to full-sized colonies.“Superorganism resilience” is not a simple substitution of dead bees by rearing more brood.Laboratory testing in the risk assessment of plant protection products bears severe weaknesses.