“In these studies we show that the honeybee colonies from 2013 remained robust to clothianidin exposure also after a second season of exposure, with no negative effect on colony development, mortality, swarming, pathogen levels or immune gene expression”, says Julia Osterman, who conducted the research as part of her MSc thesis at SLU.
“It seems that honeybee colonies can absorb potential effects on individual bees much better than bumblebee colonies or solitary bees. We also discovered that location of the oilseed rape field and year had a large influence on clothianidin residue levels in pollen, nectar and bees”, concludes Osterman.
"Our results show clear and strong relations between the use of the neonicotinoid clothianidin and the reproduction of bumblebee colonies, though not on their disease levels”, says Dimitry Wintermantel, who also conducted the research as part of his MSc thesis at SLU.
“Colonies next to oilseed rape fields sown with clothianidin-treated seeds had substantially fewer and smaller reproductives than colonies next to oilseed rape fields that were not treated with the insecticide. This may potentially affect bumblebee populations and illustrates that effects of pesticide on wild bees cannot simply be inferred from studies on honeybees”, concludes Wintermantel.
The first report, published in 2015, became an important knowledge base for the national and European discussion and legislation around the now restricted neonicotinoids.
“It was the first well replicated and controlled field study focusing on the influence of neonicotinoids on multiple species of bees”, says Maj Rundlöf, Lund University, who was scientifically responsible for the study.
The project group also involved the professors Henrik Smith, Lund University, and Riccardo Bommarco, SLU, the County Administrative Board in Skåne, the Swedish Seed and Oilseed Growers Association, two Swedish beekeepers’ organizations and a number of oilseed growers in southern Sweden that hosted the trials.
“The industry’s members in the project group had completely different hopes about the results of the study”, says Thorsten Rahbek Pedersen at the Swedish Board of Agriculture, who was the project leader.
“The most important aim was to provide data that everyone could trust. Then one has to accept and respect that one can draw different conclusions about the legal and political consequences of the results.”
Both the original publication and Wintermantel’s more detailed studies of the influence on individual bumblebees provided support for the current ban on the three neonicotinoids in crops attractive to bees. This ban led to a dramatic reduction in the cultivation of spring-sown oilseed rape in central Sweden.
“Although the cultivation of autumn-sown oilseed rape has increased, it cannot fully compensate for the reduction in the area of spring-sown oilseed rape that the ban has caused”, says Anneli Kihlstrand, CEO of the Swedish Seed and Oilseed Growers’ organization.
During summer, the Swedish Board of Agriculture will publish the results of another large project, also funded by the Swedish Civil Contingencies Agency, about the biological threats to pollinators, including those associated with the import of commercial bumblebee colonies for pollinating tomatoes, fruits and berries.
”We will conduct the largest and most ambitious screening and risk assessment associated with imported bumblebees to date in Europe”, says Joachim de Miranda, SLU, who is scientifically responsible for this study.
“This project also relies on collaboration between industry, government and academia to obtain the high quality data and analyses that our members can accept”, says Lars Hellander, board member of the Swedish National Beekeepers Association.
Rundlöf et al. (2015) Seed coating with a neonicotinoid insecticide negatively affects wild bees. Nature 521, 77–80. (www.nature.com/articles/nature14420) Wintermantel et al. (2018) Field-level clothianidin exposure affects bumblebees but generally not their pathogens. Nature Communications 9, e5446. (www.nature.com/articles/s41467-018-07914-3) Osterman et al. (2019) Clothianidin seed-treatment has no detectable negative impact on honeybee colonies and their pathogens. Nature Communications 10, e692. (www.nature.com/articles/s41467-019-08523-4)
Swedish Board of Agriculture: Thorsten Rahbek Pedersen, firstname.lastname@example.org, 070-694 37 79 Lund University: Maj Rundlöf, email@example.com, 070-92 98 524 Swedish University of Agricultural Sciences (SLU): Joachim de Miranda, firstname.lastname@example.org, 072-702 54 82 Swedish Seed and Oilseed Growers Association: Anneli Kihlstrand, email@example.com, 070-623 54 53 The Swedish Professional Beekeepers: Yngve Kihlberg, firstname.lastname@example.org, 072- 721 10 12 Swedish National Beekeepers Association: Lars Hellander, email@example.com, 070 216 33 90