Traces of a Neonicotinoid Induce Precocious Foraging and Reduce Foraging Performance in Honey Bees

There
is increasing worldwide concern about the impacts of pesticide
residues on honey bees and bee colony survival, but how sublethal
effects of pesticides on bees might cause colony failure remains highly
controversial, with field data giving very mixed results. To explore
how trace levels of the neonicotinoid pesticide imidacloprid impacted
colony foraging performance, we equipped bees with RFID tags that
allowed us to track their lifetime flight behavior. One group of bees
was exposed to a trace concentration (5 μg/kg, ppb) of imidacloprid
in sugar syrup while in the larval stage. The imidacloprid residues
caused bees to start foraging when younger as adults and perform fewer
orientation flights, and reduced their lifetime foraging flights by
28%. The magnitude of the effects of a trace imidacloprid concentration
delivered only during larval stage highlights the severity of pesticide
residues for bee foraging performance. Our data suggest that neonicotinoids
could impact colony function by imbalancing the normal age based division
of labor in a colony and reducing foraging efficiency. Understanding
this mechanism will help the development of interventions to safeguard
bee colony health.