Assessing the acute toxicity of insecticides to the buff-tailed bumblebee (Bombus terrestris audax)

T.G Emyr Davies,Rebecca J Reid,Bartlomiej J Troczka,Laura Kor,Emma Randall,Martin S Williamson,Linda M Field,Ralf Nauen,Chris Bass

doi:10.1016/j.pestbp.2020.104562

T.G Emyr Davies, Rebecca J Reid + Show 7 more

Open Access

https://doi.org/10.1016/j.pestbp.2020.104562

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Abstract

The buff-tailed bumblebee, Bombus terrestris audax is an important pollinator within both landscape ecosystems and agricultural crops. During their lifetime bumblebees are regularly challenged by various environmental stressors including insecticides. Historically the honey bee (Apis mellifera spp.) has been used as an ‘indicator’ species for ‘standard’ ecotoxicological testing, but it has been suggested that it is not always a good proxy for other eusocial or solitary bees. To investigate this, the susceptibility of B. terrestris to selected pesticides within the neonicotinoid, pyrethroid and organophosphate classes was examined using acute insecticide bioassays. Acute oral and topical LD50 values for B. terrestris against these insecticides were broadly consistent with published results for A. mellifera. For the neonicotinoids, imidacloprid was highly toxic, but thiacloprid and acetamiprid were practically non-toxic. For pyrethroids, deltamethrin was highly toxic, but tau-fluvalinate only slightly toxic. For the organophosphates, chlorpyrifos was highly toxic, but coumaphos practically non-toxic. Bioassays using insecticides with common synergists enhanced the sensitivity of B. terrestris to several insecticides, suggesting detoxification enzymes may provide a level of protection against these compounds.The sensitivity of B. terrestris to compounds within three different insecticide classes is similar to that reported for honey bees, with marked variation in sensitivity to different insecticides within the same insecticide class observed in both species. This finding highlights the need to consider each compound within an insecticide class in isolation rather than extrapolating between different insecticides in the same class or sharing the same mode of action.

Highlights

The importance of bees to agriculture and horticulture cannot be overstated
In this study we find that intrinsic tolerance to certain insecticides within a chemical class extends to the bumblebee, B. terrestris, since this pollinator shows profound differences in its sensitivity to different neonicotinoids (thiacloprid, imidacloprid (Manjon et al, 2018) and acetamiprid), and, as in honey bees, to different compounds belonging to other insecticide classes, including the pyrethroids and the organophosphates
Topical application of imidacloprid was highly toxic to B. terrestris workers, and a low synergistic effect was seen when the bees were pretreated with piperonyl butoxide (PBO) (Table 1)

Summary

Introduction

The importance of bees to agriculture and horticulture cannot be overstated. Approximately a third of all crops consumed by humans globally are bee pollinated (Delaplane and Mayer, 2000). Bombus species are the main alternative to honey bees for commercial pollination in Europe and North America (Goulson, 2010) They are utilized in the production of tomatoes and other greenhouse crops due to their ability to buzz-pollinate (Velthuis and van Doorn, 2006), whilst the longer tongues of some bumblebee species make them better at pollinating flowers with deeper corollas (Plowright and Plowright, 1997). Bumblebees start foraging earlier in the day (Stanghellini et al, 2002) and continue to forage in cold and wet weather that is unsuitable for honey bees (Corbet et al, 1993), enabling them to provide a more consistent pollination service Because they are hardier, they are better able to pollinate wild flowers in remote or fragmented locations, their impact on wild plant species is less well studied than on agricultural species (Goulson, 2010)

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