How do you decide when to spray for mosquitoes as virus response?

The Northeast Massachusetts Mosquito Control District mirrors the guidelines that the Massachusetts Department of Public Health publishes on their 2019 Arbovirus Surveillance and Response plan which can be found at this link:

https://www.mass.gov/lists/arbovirus-surveillance-plan-and-historical-data#response-plan-

You can find the virus protocol for the NEMMC District on the NEMMC website and on pages 18- 23 of the 2020 Integrated Pest and Vector Management Plan:

https://www.nemassmosquito.org/sites/g/files/vyhlif4751/f/uploads/2020_integrated_pest_and_vector_management_plan_0.pdf