Laboratory and field assays indicate that a widespread no-see-um, Culicoides furens (Poey) is susceptible to permethrin

The recent emergence of Oropouche virus (OROV) highlights the importance of understanding insecticide susceptibility in the genus Culicoides (Diptera: Ceratopogonidae). In addition to the vector of OROV, this genus contains many other species that are biting nuisances and vectors of pathogens that affect humans, livestock, and wildlife. With adulticides as the primary method of Culicoides control, there is growing concern about insecticide resistance, compounded by the lack of tools to monitor Culicoides susceptibility. We adapted the Centers for Disease Control and Prevention (CDC) bottle bioassay and field cage trial methods, typically used to monitor insecticide susceptibility in mosquitoes and formulated adulticide efficacy, to evaluate permethrin susceptibility in the widely distributed coastal nuisance species, Culicoides furens. Permethrin caused 100% mortality in C. furens in field and laboratory assays. We identified a diagnostic dose (10.75 µg) and time (30 min) that resulted in 100% mortality in CDC bottle bioassays. Additionally, we determined that no-see-um netting is an effective mesh for field cage trials, allowing for the accurate assessment of Culicoides susceptibility to ultra-low volume applications of formulated adulticides like Permanone 30-30, a widely used adulticide. These methodologies offer essential tools for assessing Culicoides susceptibility, which is crucial for managing populations of Culicoides and preventing the spread of OROV and other pathogens.