To combat the threat of vector-borne diseases, municipalities and local health departments (LHD) provide mosquito monitoring and spraying as a public health service. When mosquito abundance is too high or West Nile virus (WNV) is detected, LDHs apply broad spectrum pesticides either by air or, commonly in Columbus, by using an ultra-low volume (ULV) sprayer mounted onto a truck.
In Franklin County, very small amounts of the active ingredient (the chemical that kills mosquitoes) are applied. How small? They estimate that approximately ΒΌ of a teaspoon of active ingredient is dispersed across the size of a football field. Local health departments try to spray at dawn, dusk, or late at night when humans, pets, and pollinators are not active but mosquitoes are. The area covered by an insecticide application is estimated to be 150 feet in any direction – or a 300 foot diameter. These sprays use adulticides, meaning they target adult mosquitoes.
Due to physical barriers, spray trucks may not reach every area that contains mosquitoes. Spray trucks also use adulticides which means it does not target mosquito larvae which live in the water. Ultra-low volume truck-mounted pesticide sprays are only one tool to help manage mosquitoes. However, despite some limitations, these sprays have been shown to reduce mosquito abundance, especially when applications are repeated (2012 paper). Studies have shown that these sprays kill older mosquitoes that are more likely to be infected with WNV, thereby reducing disease transmission. (2023 paper).
Image of a Franklin County Public Health spray truck applying ultra-low volume sprays.