Country-specific effects of neonicotinoid pesticides on honey bees and wild bees

This large-scale research project spanned three European countries -- Germany, the United Kingdom and Hungary. It was designed to assess the impact on bees of planting clothianidin and thiamethoxam coated seeds for winter sown oilseed rape production. The researchers evaluated multiple endpoints for honey bees, the bumble bee Bombus terrestris and the solitary bee Osmia bicornis. Since the effects varied yet showed a general trend towards harm, researchers interpreted the findings to suggest that exposure to low levels of neonicotinoids may cause reductions in hive fitness that are influenced by a number of interacting environmental factors. Key findings include (a) queen and egg cell production for Bombus and Osmia species respectively were negatively correlated with nest residues of neonicotinoids, but were not affected by seed treatment. Bombus drone production effects were mixed with both positive and negative responses to seed treatment. Similarly, honey bee health endpoints varied between the different countries. For example, in Hungary workers treated with clothianidin were down by 24% compared to controls but no significant effect was noted from thiamethoxam treatment. In the United Kingdom hive mortality precluded a formal statistical analysis and in Germany overwintered worker numbers showed no treatment effect.   

Also worth noting is that while the neonicotinoid imidacloprid had not been used in the fields, it was detected during the study leading the researchers to conclude that impacts to bee species may be driven by persistence in the widespread landscape not simply current management methods.