The effects of nectar-nicotine on colony fitness of caged honeybees.

Nectar of many bee flowers contains secondary compounds, which are considered toxic for honeybees on repeated exposure. Although many anecdotal reports indicate the toxicity of secondary compounds to bees, only a few studies have tested the extent of toxicity at different honeybee ages, especially at the larval stages. Honeybees encounter nicotine at trace concentrations (between 0.1 and 5 ppm) in floral nectar of a few Nicotiana spp. and in Tilia cordata. Adult honeybee workers tolerate these nicotine concentrations. In controlled nonchoice feeding experiments with caged bees, we investigated the effect of nicotine on hatching success and larval and forager survival. Naturally occurring concentrations of nectar-nicotine did not affect hatching success of larvae or their survival, but the latter was negatively affected by higher concentrations of nicotine (50 ppm). Concentrations of nicotine in fresh honey samples from the hives were 90% lower than the concentrations in the offered experimental sucrose solutions. Our results indicate that honeybees can cope with naturally occurring concentrations of nicotine, without notable mortality, even when consumed in large quantities for more than 3 weeks.