Neonicotinoid residues in UK honey despite European Union moratorium

Abstract

Due to concerns over negative impacts on insect pollinators, the European Union has implemented a moratorium on the use of three neonicotinoid pesticide seed dressings for mass-flowering crops. We assessed the effectiveness of this policy in reducing the exposure risk to honeybees by collecting 130 samples of honey from bee keepers across the UK before (2014: N = 21) and after the moratorium was in effect (2015: N = 109). Neonicotinoids were present in about half of the honey samples taken before the moratorium, and they were present in over a fifth of honey samples following the moratorium. Clothianidin was the most frequently detected neonicotinoid. Neonicotinoid concentrations declined from May to September in the year following the ban. However, the majority of post-moratorium neonicotinoid residues were from honey harvested early in the year, coinciding with oilseed rape flowering. Neonicotinoid concentrations were correlated with the area of oilseed rape surrounding the hive location. These results suggest mass flowering crops may contain neonicotinoid residues where they have been grown on soils contaminated by previously seed treated crops. This may include winter seed treatments applied to cereals that are currently exempt from EU restrictions. Although concentrations of neonicotinoids were low (<2.0 ng g-1), and posed no risk to human health, they may represent a continued risk to honeybees through long-term chronic exposure.

Fig 1. Location of UK honey samples.

The two maps show the location of honey samples collected in 2014–15 superimposed over the cover of all arable crops (A) and oilseed rape (B).

Fig 2. Change in neonicotinoid residues in honey pre- and post-moratorium.

The first graph (A) shows the change in average (±SE) combined (clothianidin, thiamethoxam and imidacloprid) residues found in honey over time. Due to the limited number of samples the pre-moratorium period is combined into a single value. The second graph (B) shows how the proportion of honey samples containing neonicotinoid residues changed over time. Note that residues of more than one neonicotinoid type may appear in a single honey sample. As such the proportion of samples containing either clothianidin, thiamethoxam or imidacloprid has been scaled so that when combined it does not exceed the proportion of honey samples containing neonicotinoid residues of any type. Where N = the number of honey samples for a particular time period.

Fig 3. Response of combined neonicotinoid residues in honey to land use.

The graphs show the back transformed model predictions (±SE) for the response of combined neonicotinoid residues found in honey to (A) oilseed rape cover, (B) winter sown cereals and (C) total arable cover. All honey was collected in 2015 during the first year where the use of neonicotinoids seed treatments had been banned on mass flowering crop in the EU. All percentage covers are within 2 km radii of individual hives. Neonicotinoid residues represent the combined concentration of imidacloprid, thiamethoxam and clothianidin.