So I can't see in that study where they correlate actual field concentrations to what they're applying to the test insects. From what I can tell, they're using very high concentrations and observing reduced melanization. Interestingly, in lower concentrations, there's a tendency for the mosquitos to develop a better response to the infection, presumably because the survivors are less susceptible.

Further, while the 10 mM-treated mosquitoes had the worst survival outcome, the mosquitoes that survived the drugging showed low susceptibility to P. falciparum infection. These observations suggest a potentially interesting effect whereby very high concentrations of glyphosate reduce mosquito survival, but bolster the immune system or general physiology of survivors, which then allows them to resist P. falciparum infection with greater success. Alternatively, very high glyphosate treatment could be selecting for mosquitoes within the population more resistant to P. falciparum infection.

What you normally see in these studies is that they have to directly apply concentrations much, much higher than found in the field to develop a response. The runoff levels are tested to be in the nM range, but they're applying 10-50 mM to each insect directly injected. Even if they're in the field and encountering mM concentrations as applied, contact with an insect probably isn't going to transfer much to the bloodstream as there's no direct transfer pathway for animals.