Glyphosate is the world’s most widely used herbicide. The commercial success of this molecule is due to its non-selectivity 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 non-target 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.

Lab experiments

Experiment 1: pure glyphosate and glyphosate-based herbicides

The purpose of this experiment was to test the impact of pure glyphosate and glyphosate-based herbicides (formulation), on mosquito life history traits and susceptibility to malaria parasite infection.

Experiment 2: pure glyphosate and food limitation

The purpose of the second experiment was to evaluate the impact of larval exposure to glyphosate associated to a nutritional stress on mosquito life history traits and susceptibility to malaria parasite infection.

For both experiments we measured the impact of glyphosate exposure and nutritional stress on:

Larvae survival rate, developpement time, adult size, blood meal rate, blood meal size, fecundity, susceptibility to malaria parasite infection (infection probability and parasite burden)