A novel class of pesticides, expected to be a key replacement for neonicotinoids, may have sub-lethal effects on bumblebee colonies, reports a paper published online in Nature this week.

Sulfoximine-based pesticides have been shown to be effective in targeting neonicotinoid-resistant species and have been approved for use in China, Canada and Australia, with licence applications progressing in several EU member states. However, the two classes of pesticide share a common biological mode of action and the sub-lethal effects of sulfoximines on pollinators have not yet been fully investigated.

Harry Siviter and colleagues found that bumblebee colonies exposed to the sulfoximine pesticide sulfoxaflor in a laboratory setting produced significantly fewer workers and reproductive male bumblebees once released into a field setting. Twenty-five colonies were exposed to conservative doses of sulfoxaflor for two weeks during the early growth phase, and differences between these colony populations and the 26 control colonies began to emerge 2-3 weeks post-exposure and persisted until the end of the colony lifecycle. Treated colonies experienced a 54% reduction in reproductive offspring, suggesting that the exposure of a small cohort of bumblebees in the early stages of a colony’s life history may have long-term consequences for colony fitness. However no changes in foraging behaviour or pollen load were observed.

The authors suggest that sulfoxaflor exposure could lead to similar environmental impacts on pollinators as neonicotinoids in the absence of evidence-based legislation. They call for regulatory bodies to assess both the lethal and non-lethal consequences of novel insecticides before licencing them for use.