Mosquito larval and adult collections in Stratford and Milford, Connecticut, United States 2019 - 2020

Background Mosquito larval control through the use of insecticides is the most common strategy for suppressing West Nile virus (WNV) vector populations in Connecticut (CT), United States. To evaluate the ability of larval control to reduce entomological risk metrics associated with WNV, we performed WNV surveillance and assessments of municipal larvicide application programs in Milford and Stratford, CT in 2019 and 2020. Each town treated catch basins and non-basin habitats (Milford only) with biopesticide products during both WNV transmission seasons. Adult mosquitoes were collected weekly with gravid and CO2-baited light traps and tested for WNV; larvae and pupae were sampled weekly from basins within 500m of trapping sites, and Culex pipiens larval mortality was determined with lab bioassays of catch basin water samples. Results Declines in 4th instar larvae and pupae were observed in catch basins up to 2-weeks post-treatment, and we detected a positive relationship between ...