The large-scale field study was carried out in 2012; its results were published last month. The experiment was designed to determine whether exposure to clothianidin seed-treated Canola (oilseed rape) has any adverse impacts on honey bees.
Colonies were placed in clothianidin seed-treated or control canola fields during bloom, and thereafter were moved to an apiary with no surrounding crops grown from seeds treated with neonicotinoids.
Colony weight gain, honey production, pest incidence, bee mortality, number of adults, and amount of sealed brood were assessed in each colony throughout summer and autumn. Samples of honey, beeswax, pollen, and nectar were regularly collected, and samples were analyzed for clothianidin residues.
Overwintering success did not differ significantly
The conclusion: Colonies were vigorous during and after the exposure period, and no effects of exposure to canola seeds, treated with clothianidin, were detected on any endpoint measurements.
Overwintering success did not differ significantly between treatment and control hives, and was similar to overwintering colony loss rates reported for the winter of 2012–2013 for beekeepers in Ontario and Canada.
“Our results suggest that exposure to canola grown from seed treated with clothianidin poses low risk to honey bees,” say the study authors.