Bumblebee queens exposed to a common neonicotinoid pesticide are less able to form new colonies, which could lead to collapses in wild populations, reports a paper published online this week in Nature Ecology & Evolution.
Neonicotinoid pesticides are widely used in agriculture, but in recent years both laboratory and field studies have implicated them in the decline of bee populations, leading to an EU moratorium on their use. However, we do not yet fully understand the connection between adverse effects of neonicotinoids on individual bees or colonies and declines at the population level.
Gemma Baron and colleagues exposed Bombus terrestris queens to field-realistic doses of the neonicotinoid, thiamethoxam. They find this resulted in a shift in the timing of new colony formation and a 26% reduction in the number of queens that laid eggs. They then used mathematical modelling to predict the effects of this 26% reduction on the whole population, finding the chance of a population collapsing after widespread thiamethoxam use to be at least 28%.
Colony formation is a crucial stage in the life cycle of bees, and these results show that this stage is particularly sensitive to the negative effects of neonicotinoids. The authors note that further research is needed to explore the long-term impacts that the observed reduction in egg laying has on colony success and population dynamics in the field.