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There is an on-going need to develop new insecticides that are not compromised by resistance and that have improved environmental profiles. However, the cost of developing novel compounds has increased significantly over the last two decades. This is in part due to increased regulatory requirements, including the need to screen both pest and pollinator insect species to ensure that pre-existing resistance will not hamper the efficacy of a new insecticide via cross-resistance, or adversely affect non-target insect species. To add to this problem the collection and maintenance of toxicologically relevant pest and pollinator species and strains is costly and often difficult. Here we present Fly-Tox, a panel of publicly available transgenic Drosophila melanogaster lines each containing one or more pest or pollinator P450 genes that have been previously shown to metabolise insecticides. We describe the range of ways these tools can be used, including in predictive screens to avoid pre-existing cross-resistance, to identify potential resistance-breaking inhibitors, in the initial assessment of potential insecticide toxicity to bee pollinators, and identifying harmful pesticide-pesticide interactions., Graphical abstract Unlabelled Image, Highlights • Drosophila melanogaster is a powerful model system to study cytochrome P450-mediated insecticide tolerance. • Fly-tox comprises a panel of transgenic D. melanogaster lines expressing P450s from insect pest and pollinator species. • Fly-tox can be used in numerous ways to characterise the role of pest/pollinator P450s in insecticide metabolism. • We describe the applications of Fly-Tox and provide detailed protocols on its use. • The benefits and limitations of the system are discussed.

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., Graphical abstract Unlabelled Image, Highlights • Acute toxicity of popular insecticides to Bombus terrestris audax was assessed. • Compounds from 3 major classes were tested in topical and oral bioassays. • Bioassays with different synergists were done for each compound. • Results show stark differential toxicity of insecticides within the same class.