When the EU Commission decided to impose a restriction on three neonicotinoids in 2013, it attached great weight to a few laboratory-based studies which showed potentially sub-lethal effects on honey bees or bumbles bees.
These studies were recently published in high impact journals.
Norman Carreck, bee researcher at the University of Sussex, has now presented a review of these primary source studies with the aim to determine whether the laboratory results would also apply under field conditions. Summing up his findings he says:
“Here we review the three key dosage factors (concentration, duration and choice) relevant to field conditions, and conclude that these have probably been over estimated in many laboratory based studies.”
Looking at the concentration rates used in some of these studies, Carreck finds that rather than being realistic to normal field conditions, “they seem more representative of a ‘worst case’ scenario”. As to the duration of exposure, his analysis showed that some studies treated bees with large single doses equivalent to much longer field exposure. To highlight the difference, the study compares this to “the different effects on a human of drinking a bottle of whisky over 1 hour, 24 hours, or longer.”
The third key dosage factor examined was choice. In the field, bees generally have a choice of several food sources, while in the laboratory it is frequently assumed that the entire colony would forage on a treated crop. “This is not the case”, says Carreck, pointing to UK studies that show wildflowers to be the main pollen collected by the rural hives.
Summing up his results, Carreck warns that an unnecessary moratorium on neonicotinoids not only fails to help bees, but could make matters worse, because farmers would revert to older plant protection technologies that require more frequent spraying, are more damaging to wildlife and were not subjected to today’s rigorous registration procedures.
He concludes by saying: “It is self-evident that insecticides can kill insects, and it is unsurprising that sub-lethal doses can weaken colonies or disorient individual bees. But, as noted by Paracelsus, the dose makes the poison.”
The study was published in the "Journal of Apicultural Research".