241 - Insecticide resistance cage trial results for Eastern Equine Encephalitis vectors in Massachusetts

Abstract: Insecticide resistance is a cause for concern in the North Atlantic region given the limited availability of mosquito control pesticides. The states are working to expand upon ongoing insecticide resistance testing using bottle bioassays conducted by the Northeast Regional Center for Excellence in Vector-borne Disease Teaching and Evaluation Center by characterizing the susceptibility of important Eastern Equine Encephalitis (EEE) vector species to available adulticide products. Commonly used aerial and truck-based adulticide products were evaluated in a limited caged field study conducted in Massachusetts with technical support provided by Clarke. The mosquito species of concern included Culiseta melanura, Coquillettidia perturbans and other human biting vector species. Each of the wild-caught mosquito populations tested showed a high degree of susceptibility to the adulticide products when exposed to field-relevant application rates and droplet spectra. The average mortality rate of mosquitoes tested exceeded 90% for every replicate of each product. This degree of mortality met or exceeded that of a susceptible colony of Culex quinquefasciatus used as a control population. The results of this field study contributed to confidence in adulticide product selection for local mosquito control districts and the state during a EEE outbreak while also highlighting the difficulties of conducting these types of caged field studies.