Glyphosate is the world's most widely used herbicide. The commercial success of this molecule is due to its nonselectivity and its action, which would supposedly target specific biosynthetic pathways found mainly in plants. Multiple studies have however provided evidence for high sensitivity of many nontarget species to glyphosate and/or to formulations (glyphosate mixed with surfactants). This herbicide, found at significant levels in aquatic systems through surface runoffs, impacts life history traits and immune parameters of several aquatic invertebrates' species, including disease‐vector mosquitoes. Mosquitoes, from hatching to emergence, are exposed to aquatic chemical contaminants. In this study, we first compared the toxicity of pure glyphosate to the toxicity of glyphosate‐based formulations for the main vector of avian malaria in Europe, Culex pipiens mosquito. Then we evaluated, for the first time, how field‐realistic dose of glyphosate interacts with larval nutritional stress to alter mosquito life history traits and susceptibility to avian malaria parasite infection. Our results show that exposure of larvae to field‐realistic doses of glyphosate, pure or in formulation, did not affect larval survival rate, adult size, and female fecundity. One of our two experimental blocks showed, however, that exposure to glyphosate decreased development time and reduced mosquito infection probability by malaria parasite. Interestingly, the effect on malaria infection was lost when the larvae were also subjected to a nutritional stress, probably due to a lower ingestion of glyphosate.

Culex pipiens complexes play an important role in the transmission of a wide range of pathogens that infect humans, including viruses and filarial worms, as well as pathogens of wildlife, such as the avian malaria parasite (Plasmodium spp.). Numerous biotic and abiotic stresses influence vector-borne pathogen transmission directly, through changes in vector density, or indirectly by changing vector immunocompetence, lifespan, or reproductive potential. Among these stresses, mosquito exposure to sublethal doses of pesticides could have important consequences. In addition to being exposed to pollutants in aquatic breeding sites, mosquitoes can also be exposed to chemicals as adults through their diet (plant nectar). In this study, we explored the impact of mosquito exposure at the larval and adult stages to one of the most commonly used pesticides, imidacloprid, a chemical belonging to the class of the neonicotinoids, on a set of life history traits ranging from development time to fecundity. We also studied the impact of this pesticide on the susceptibility of mosquitoes to infection by the avian malaria parasite, Plasmodium relictum. Surprisingly, we observed no effects of imidacloprid on any of the parameters examined. This result highlights the fact that Culex pipiens mosquitoes do not appear to be susceptible to imidacloprid when exposure doses are close to those measured in the field.

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