Identities, concentrations, and sources of pesticide exposure in pollen collected by managed bees during blueberry pollination

Authors: Graham, Kelsey; MILBRATH, MEGHAN - Michigan State University; ZHANG, YAJUN - Michigan State University; SOEHNLEN, ANNUET - Michigan State University; BAERT, NICOLAS - Cornell University; MCART, SCOTT - Cornell University; ISAACS, RUFUS - Michigan State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2021
Publication Date: 8/19/2021
Citation: Graham, K.K., Milbrath, M.O., Zhang, Y., Soehnlen, A., Baert, N., McArt, S., Isaacs, R. 2021. Identities, concentrations, and sources of pesticide exposure in pollen collected by managed bees during blueberry pollination. Scientific Reports. 11. Article 16857. https://doi.org/10.1038/s41598-021-96249-z.
DOI: https://doi.org/10.1038/s41598-021-96249-z

Interpretive Summary: Bees are critical for pollination of many crops, yet bees face risks to their health while on farms, such as exposure to pesticides. Pesticides are needed for the control of many plant pests and pathogens, which are sometimes prevalent during bloom when bees are visiting the crop for food (pollen and nectar). Understanding the levels and sources of pesticide exposure for bees during bloom is therefore critical for reducing risks to bee health. Honey bees and bumble bees are both used for highbush blueberry pollination, and both collect pollen to feed their young. We collected honey bee and bumble bee collected pollen and screened these samples for 259 pesticides, which gave us a snapshot of the current exposure while bees are in the fields. Of the 188 pollen samples we collected, all samples had pesticides, with an average of 22 difference pesticides (active ingredients, AIs) in each sample. Honey bees had more pesticide AIs in their pollen on average compared to bumble bees; however, bumble bees had higher concentrations of pesticides on average in their pollen. We also found that the majority of AIs we detected in both honey bee and bumble bee pollen are not sprayed on the farms where bees were located and are instead coming from the surrounding areas. However, many of individual detections of AIs with high concentrations were from pesticides used on the farms where bees were located. These results highlight the need for integrated farm and landscape-scale stewardship of pesticides to reduce exposure to managed pollinators during pollination.

Technical Abstract: Bees are critical for crop pollination, but there is limited information on levels and sources of pesticide exposure in commercial agriculture. We collected pollen from foraging honey bees and bumble bees returning to colonies placed in blooming blueberry fields with different management approaches and located across different landscape settings to determine how these affect pesticide exposure. We also identified the pollen and analyzed whether pesticide exposure was correlated with corbicular load composition. Across 188 samples collected in two years, we detected 80 of the 259 pesticide active ingredients (AIs) screened for using a modified QuEChERS method. Detections included 28 fungicides, 26 insecticides, and 21 herbicides. All samples contained pesticides (average 22.0 AIs), with pollen collected from bees on conventional fields having significantly higher average concentrations than those on unmanaged fields. Pollen collected by honey bees had more AIs than bumble bees, whereas samples from bumble bees had higher average concentrations, likely reflecting differences in foraging behavior. Blueberry pollen was more common in pollen samples collected by bumble bees (25.9% per sample) than honey bees (1.8%), though pesticide concentrations were only correlated with blueberry pollen in honey bees. Pollen collected at farms with more blueberry in the surrounding landscape had higher pesticide concentrations, mostly AIs applied for control of blueberry pathogens and pests during bloom. However, 75% of detected AIs are not registered for use on blueberry at any time of the year, suggesting these bees are exposed to the majority of AIs outside the fields and farm they are expected to pollinate. Our results highlight the need for integrated farm and landscape-scale stewardship of pesticides to reduce exposure to managed pollinators during crop pollination.