PULLMAN, WA - The latest good news on the pollinator front arrived in the form of research results from a team of scientists at Washington State University (WSU). The principal investigators (T. J. Lawrence, E. M. Culbert, A. S. Felsot, V. R. Hebert, and W. S. Sheppard) set out to conduct a survey and risk assessment of honey bee colony exposure to four neonicotinoid insecticides (clothianidin, dinotefuran, imidacloprid, and thiamethoxam) in urban, rural, and agricultural settings.
Wax and beebread (pollen stored in hives) were collected from a total of 149 apiaries throughout Washington State in 2013 and 2014. The maximum residue detected over all the samples collected was 3.9 ppb of imidacloprid, which is far lower than the EPA’s recently established threshold of 25 ppb (as reported in the last issue of Washington Impact). The risk quotient (in the WSU study) suggested a low potential for negative effects caused by those four neonicotinoids on bee behavior or colony health.
A key component to the WSU study was to define each apiary’s location as urban, rural, or agricultural to better characterize the impact of neonicotinoids in these three very different landscapes. Not surprisingly, more residues were detected in samples collected from agricultural landscapes. About 50 percent of the beebread samples collected from apiaries in agricultural landscapes contained clothianidin and/or thiamethoxam. For comparison, residues were detected in only 5 percent of the apiaries located in urban and rural areas, undoubtedly including apiaries surrounded by managed landscapes.
Of all the samples with measurable residues, whether from a rural, urban, or agricultural landscape, the researchers found that none of the samples contained residues at levels high enough to negatively impact honey bee health. Again, the maximum residue level detected in this study was 3.9 ppb of imidacloprid, well below the limit considered as causing adverse effects, based on EPA’s latest risk assessment. The authors of this study concluded that their data suggest “a nil risk of sublethal effects” in rural and urban landscapes and a very low risk from exposure in agricultural landscapes.
This study is important and relevant for a few reasons. First, the study examines the impact of neonicotinoids at the colony level (as opposed to individual bees). Second, the study did not restrict honey bees to one food source (presumably spiked with a neonicotinoid, as in some recent studies). Therefore, the WSU study more closely reflects real-world situations where bees forage. Third, this study separated samples collected from apiaries in three different landscapes, providing critical data on the level of impact of neonicotinoid-treated landscape plants to honey bee colonies. Full results will be published in the Journal of Economic Entomology.
In other pertinent pollinator news: the European Food Safety Authority (EFSA) began a full review of the scientific evidence and risk assessment of the impact of clothianidin, imidacloprid, and thiamethoxam on pollinator health, to be completed by January 2017. In 2013, the EFSA issued a moratorium on these three neonicotinoids and cited a clear lack of data on impacts. New data and research will be used to establish a risk assessment.