Nicotine in nectar: Consumption and perception by honey bees (Apis mellifera) and its effect on their survival

The effects of nicotine on honey bees were tested as a model system to understand possible roles of secondary compounds in floral nectar. Eight honey bee colonies were tested for their preference among six feeders containing all the combinations between two sugar concentrations (20% or 50%) and three nicotine concentrations (0, 5 or 50 ppm). Individual bees from these colonies were tested for the effect of nicotine on learning performance using the proboscis extension response paradigm. Afterwards, half of the tested colonies were fed for three weeks with pure sucrose solution and the rest were fed with sucrose solution enriched with nicotine. Then the bees were tested again for preference and learning. In addition, harnessed bees were tested for their daily food consumption and survival while being fed with sucrose solution with various nicotine concentrations. We found that nicotine repelled bees, but repellency was partially overcome by increased sugar concentration and that early exposure to nicotine may decrease its repellency. Nicotine added to reward did not affect learning performance and survival, but at high concentration it decreased food consumption. We concluded that nicotine concentration in the range that naturally occurs in nectar repels bees. Higher concentrations are more repellent and reduce consumption. Interestingly, prolonged exposure to nicotine resulted in habituation to nicotine. Thus, nicotine in floral nectar may serve as a repellent for occasional visitors, but less so to regular visitors, which would be more efficient pollinators.