Assessing permethrin susceptibility of field-collected biting midges in Florida and evidence for resistance evolution...

Culicoides biting midges (Diptera: Ceratopogonidae) remain economically important dipteran pests of livestock and other animals worldwide. They are known for their blood-feeding nuisance behaviours, but also serve as biological vectors of several animal pathogens, including bluetongue virus, epizootic hemorrhagic disease virus and vesicular stomatitis virus. Efforts to limit biting midge access to target hosts such as cattle and sheep have relied predominantly on insecticide use. However, research regarding biting midge insecticide efficacy largely has been focused on animal and barrier treatments using formulated commercial products, with little effort to identify local endemic species level susceptibility to specific active ingredients. This study was conducted to determine the susceptibility of biting midges under laboratory and field conditions, as well as to determine the potential for insecticide resistance development in these pests. Under laboratory conditions, the susceptibility of a laboratory-reared biting midge colony (Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae)) was significantly less than wild Culicoides spp. Similarly, wild Culicoides spp. also were significantly more susceptible than wild mosquitoes when exposed to an ultra-low volume permethrin application under field conditions. Additionally, a long-established C. sonorensis colony subjected to permethrin selection under laboratory conditions suggested that insecticide resistance development in this pest could occur in field populations if pressured. This is the first account of the potential for insecticide resistance development in Culicoides. The implications of Culicoides spp. insecticide resistance and the lack thereof in assessed field populations are discussed.