Heavy pesticide use in Wake County fuels resistant mosquitoes

Two NC State studies found that mosquitoes in Wake County are rapidly evolving resistance to pyrethroids, the insecticides most often used against adult mosquitoes, with the strongest signal in wealthier neighborhoods where backyard spraying is common. Researchers linked the pattern to local mosquito-control pressure, raising the risk that a tool used heavily in one part of the county becomes less effective for everyone else.

The studies focused on tiger mosquitoes, Aedes albopictus, and found mutations associated with pyrethroid resistance. One paper described highly focal resistance in a suburban Raleigh area, a pattern researchers said may be tied to peri-domestic mosquito-control activities, the sprays and treatments used around homes and yards.

Martha Burford Reiskind, an associate professor at NC State, said, “Homeowners with money will pay to spray for mosquitoes, which selects for localized resistance.” That matters in Wake County because the county's public-health program says it works to prevent and control communicable diseases and vector-borne illness among people who work, eat, play and live here.

Wake County's mosquito-prevention work has to operate through the long, humid stretch of summer, when mosquitoes are already abundant and resistance can make repeated spraying a weaker answer. The county's health and human services page frames mosquito control as part of broader disease prevention, but the NC State findings suggest broad reliance on the same chemical class can backfire if mosquitoes survive enough exposure to pass resistance along.

The immediate pressure is on how mosquito control is targeted before peak mosquito season. In affluent parts of Wake, more backyard spraying may be doing the opposite of what residents want, preserving mosquitoes that can shrug off pyrethroids and leaving fewer options when the county needs to knock down mosquito populations quickly.