Assessment of neonicotinoid residues in National Honey Monitoring Scheme honey samples from 2021 & 2022

Woodcock, Ben A. ORCID: https://orcid.org/0000-0003-0300-9951; Harrison, Sam ORCID: https://orcid.org/0000-0001-8491-4720; Dos Santos Pereira, Gloria ORCID: https://orcid.org/0000-0003-3740-0019; Sleep, Darren ORCID: https://orcid.org/0009-0002-1128-1883; Savage, Joanna ORCID: https://orcid.org/0000-0002-5280-5148; Pywell, Richard F. ORCID: https://orcid.org/0000-0001-6431-9959. 2024 Assessment of neonicotinoid residues in National Honey Monitoring Scheme honey samples from 2021 & 2022. UK, Defra. (Unpublished)

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Abstract/Summary

Pollinating insects play an important role in ecosystems and provide a crucial service to the agricultural sectors, worth £0.5 billion in terms of UK agricultural yield improvements. The causes of pollinator declines are diverse, although agriculture use of pesticides is a potentially significant factor, albeit one likely interacting with a range of other environmental drivers. Understanding real-world exposure to pesticides has an important role to play in mitigating the risks posed by post-regulatory approval of pesticides. This includes derogations applied to otherwise restricted use active ingredients. Neonicotinoid systemic seed treatments (thiamethoxam, clothianidin and imidacloprid) have been widely associated with risks to insect pollinators because of residues being expressed in the nectar and pollen of flowering plants. While risk was originally perceived to be associated with treated flowering crops (e.g., oilseed rape), the non-target uptake by in-field weeds or wild flowering plants growing on soils contaminated with neonicotinoid residues has also been identified as a problem. This risk resulted in the total withdrawal for in field use of neonicotinoids in 2018. Unfortunately, this withdrawal left a significant gap in the capacity of farmers to protect crops from pests with resistance to remaining chemical control methods, in particular pyrethroids. This was the case for sugar beet crops where Beet Yellow Virus transmission via an aphid vector (the target of the neonicotinoids) was identified as causing ~25 % crop losses in 2020 worth an estimated £67 million. In 2022 the UK Government granted a derogation for the use of the neonicotinoid seed treatment (thiamethoxam - sold as Cruiser SB) on sugar beet for the four major English counties growing this crop - West & East Norfolk, West Suffolk and East Nottinghamshire. Unlike oilseed rape, sugar beet does not flower before harvesting and so is perceived to be a lower risk crop in terms of pollinators. Nevertheless, there are risks of pollinators being exposed to resides expressed in the pollen and nectar of non-crop weed species growing at the edges of fields. To address these risks a series of mitigation measures were required, including: 1) to avoid the prophylactic use of thiamethoxam (i.e. application without significant expectation of a pest problem), the pesticide would only be authorised if there was a high viral risk, defined as a predicted viral incidence rate that exceeded 19%. 2) to reduce the risk of expressing neonicotinoid residues in the pollen and nectar in following crops only one treated sugar beet crop could be grown in a field and mass flowering crops attractive to pollinators, such as oilseed rape or beans, were prohibited in the following 46 months; and 3) non-target plants growing at the field edge were not allowed to flower. The National Honey Monitoring Scheme (NHMS) is a UK scale network of beekeepers coordinated through the UK Centre for Ecology & Hydrology and funded though the AgZero+ project (NERC NE/W005050/1 AgZero+: Towards sustainable, climate-neutral farming). Through this scheme > 1000 honey samples are collected across the UK each year. Honeybees are a focal model system for regulatory assessments of pesticides which forage over large areas and so are exposed to pesticides at landscape scales. As such, quantification of pesticide residues within these samples are currently being used to develop a Defra H4 indicator to assess exposure and adverse effects of chemicals on wildlife in support the government 25 Year Environment Plan. In this report, we present a comparison of neonicotinoid residues in honey samples collected though the NHMS in 2021 and 2022 from those counties granted derogations for the use of thiamethoxam as a seed treatment on sugar beet in 2022. In each year, 50 honey samples were selected from areas within 2 km of sugar beet crops and analysed for residues of thiamethoxam (the derogation active ingredient in Cruiser SB), clothianidin (a currently withdrawn neonicotinoid and a metabolite of thiamethoxam) and imidacloprid (a currently withdrawn neonicotinoid). We compared these residues between pre- and derogation years to understand how risk to insect pollinators (with a focus on honeybees) has changed. To do this we derived predicted residue concentrations in nectar and linked these to levels of concern intended to predict the likelihood that environmental concentrations of these neonicotinoids posed a risk to honeybees. We also derived probabilistic species sensitivity distribution across a range of bee species to quantify whether the predicted environmental concentrations of neonicotinoids (thiamethoxam, clothianidin and imidacloprid) posed a hazard to bee pollinator assemblages.

Item Type:	Publication - Report (Project Report)
UKCEH and CEH Sections/Science Areas:	Biodiversity (Science Area 2017-24) Pollution (Science Area 2017-24)
Funders/Sponsors:	Defra
Additional Information:	On publication, full text should be available via Defra website.
NORA Subject Terms:	Ecology and Environment Zoology
Date made live:	04 Dec 2025 12:45 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/540674

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