In a new study on truck-mounted mosquito-control sprays, the proportion of local mosquito populations that could potentially carry West Nile virus decreased after treatments, even though overall numbers of mosquitoes weren’t affected—an “invisible” but positive sign about the utility of such mosquito management efforts. Here, study lead author Kristina Lopez, Ph.D., of the Department of Entomology at the University of Wisconsin at Madison, checks a mosquito trap where local mosquito populations were monitored after insecticide applications. (Photo by Justin Harbison, Ph.D.)