Pollinators' exposure to pesticides in the Swedish agricultural landscape

Published 11 January 2023

Honey bee (Apis mellifera) collecting pollen and nectar from an apple flower in a Scanian apple orchard in May. Photographer: Maj Rundlöf

Plant protection products are used in agriculture for more predictable and better harvests. Honeybees and other flower-visiting insects are exposed to residues of these substances when they collect pollen and nectar in the landscape. According to a new study from the Swedish University of Agricultural Sciences (SLU)
and Lund University, pollen was found to contain high concentrations of many substances compared to nectar and air. Continuous analysis of residues in pollen could therefore be a way to monitor the risk of plant protection products for flower-visiting insects.

The aim of the project, AirBeeSafe, was to increase knowledge about the exposure of pollinating insects to plant protection products in the agricultural landscape. That is, which substances they are exposed to in the environment, at what concentrations, when and where.

In the summers of 2020 and 2021, the project group placed honey bee colonies in eight locations around Scania. Honeybees seek food over large areas and from a variety of plant species, and their collected pollen and nectar were used to measure their exposure to different pesticides. In addition, air samples were collected at each sampling location.

Pollen can be a risk to bees

Mikaela Gönczi is the director of SLU Centre for Pesticides in the Environment (CKB):
- An interesting result is that few substances represent the greatest risk. However, for several of those substances, the approval for use has recently expired, so we will probably see changing risks going forward.

The study shows that pollen contains the most substances, often in high concentrations, from plant protection products. Some substances also had high toxicity – mainly insecticides. The substance that stood out as the most risky, with both high concentrations and high toxicity for honey bees, was the insecticide indoxacarb. However, it has been banned for use since the study was conducted.

Pollen collected by honey bees in pollen traps from four hives. There can be great variation in color between pollen from different plant species. Photo: Theresia Widhalm, Lund University — Pollen collected by honey bees in pollen traps from four hives. Photo: Theresia Widhalm

The findings in nectar were fewer and the concentrations were lower than in pollen. This is positive because nectar is the main source of energy for many flower-visiting insects.

The most common substance found in the air, which also occurred in the highest concentrations, was the herbicide prosulfocarb, which is relatively non-toxic to bees. The analysis of the air samples shows that the risk of plant protection products via the air increases with more arable land there in the area.

Analysing the air distinguish this study from others

Plant protection products have been measured to various extents in several previous studies, both Swedish and international. What is special about this particular study, is that the researchers not only analysed concentrations in pollen and nectar, but also in air collected near the bee hives.

The combination of analysing pollen, nectar and air was very interesting, says Maj Rundlöf, researcher at BECC:

- Since pollinators spend a large part of their lives flying in these environments, it is relevant to investigate plant protection products in the air as well. Pollen and nectar have been investigated previously in relation to bees, while air is less studied as an exposure route.

The honey bee is a useful model species for exposure

The study is done with the honey bee (Apis mellifera) as a model species. Honeybees are useful as a model species for exposure since they can be kept by beekepers, and large amounts of pollen can be collected from them without significantly disturbing the bee colony.

- If pollen collected by honeybees can be used to monitor risks linked to plant protection products for flower-visiting insects more generally, then we could quantitatively follow up relevant policy objectives on a non-toxic environment and reductions of environmental risks with plant protection products, says Maj Rundlöf.

More information about the study

Funding and partners

The project was carried out in collaboration between the SLU Center for Chemical Pesticides in the Environment (CKB) and the Department of Biology, Lund University, as well as farmers and beekeepers. Funding was provided by the Swedish Environmental Protection Agency and the strategic research area BECC, Biodiversity and Ecosystem services in a Changing Climate.