Reducing the population of adult mosquitoes with public health pesticides (adulticides) that are registered by the US Environmental Protection Agency (US EPA) will be done if necessary to prevent human illness or suppress a heavy nuisance infestation of mosquitoes. The decision to use mosquito control applications either by truck-mounted, backpack or aircraft application equipment will be based on surveillance information or the documentation of West Nile virus activity at a level that indicates a threat to human health. Either Adulticiding (ULV) or Larvicide (WALS) will be concentrated in areas most at risk for disease occurrence or where travel-related mosquito-borne disease cases have been identified.
If weather conditions are not favorable, or if there are operational delays, the treatment may be postponed or delayed. Treatments may continue or resume in the following weeks with continued West Nile virus activity.