A mosquito goes through four distinct stages during its life cycle: egg, larva, pupa and adult. PERM-X UL 4-4 is an adulticide, which means that it affects mosquitoes in the adult life cycle only. Mosquito control programs typically apply treatment by use of an aerosol sprayer, and St. Charles County utilizes a truck-mounted method fashioned with an ultra-low volume (ULV) sprayer. We choose to apply this treatment during the late evening/night hours, when mosquitoes are most active and pollinators are most inactive. ULV sprayers dispense very fine aerosol droplets that contain small quantities of active pesticide ingredients that stay aloft and eliminate mosquitoes on contact. The application area extends almost 300 feet from the vehicle — so even though spraying may be done from the street; it is designed to reach backyard areas. St. Charles County began using PERM-X UL 4-4 for insect treatment in 2023.