In an effort to protect public health and improve the quality of life for our residents, the City of Ballwin
contracts with St. Louis County Vector Control Services for control of mosquito larvae. Although no method of mosquito control is 100 percent effective, larvicide does offer some control of the mosquito
population. Trap sites are set throughout St. Louis County and checked for mosquitoes. Mosquitoes
collected at these sites are brought into a laboratory setting where they are counted and identified by species. Surveillance data allows St. Louis County Vector Control Services to focus reduction measures in areas where high numbers of medically significant mosquito species are present, and/or where mosquitoes are actively carrying disease.

Previous Methods
For several years, the Public Works Department provided mosquito adulticide services, a weekly application of mosquito control spray in residential areas throughout the City from late May to mid-September. In August 2025, the Board of Aldermen voted unanimously to discontinue this service. They noted adulticide services were not effective in reducing the mosquito population and instead harmed other, beneficial insects.

The Public Works Committee discussed this issue during several meetings in 2025 and previous years. Effectiveness, not cost, was a key factor in the decision to discontinue the service. The chemical had to make direct contact with the mosquitoes to be effective. The spraying had to be done in the evenings when mosquitoes are active but also at a time when other insects would not be harmed. Many residents opted out of the service, so the operator would turn off the sprayer when reaching the addresses of homeowners who opted out. Dispersion was also a factor in the decision. The weather conditions at the time of spraying had to be perfect for the chemical to reach beyond the street or front yard.

Tips for Reducing Mosquitoes on Your Property
• We encourage residents to keep your lawns mowed, keep rain gutters clean, remove standing water on
your private property and complete other preventive measures to reduce potential mosquito breeding
locations. Additional tips:
• Clean up trash or litter around your yard
• Remove or regularly flush places where water can collect around your home, including pet dishes, bird
baths, fountains, flower pots and old tires
• Don’t let water accumulate in rain gutters, piles of leaves, or in vegetation
• Remove sources of standing water in and around your home in plant pot saucers, pool tarps, etc.
• Tightly cover water storage containers (rain barrels, etc.)
• For containers without lids, use wire mesh with holes smaller than an adult mosquito

Remove Standing Water Where Mosquitoes Lay Eggs

• Once a week, empty and scrub, turn over, cover, or throw out any items that hold water like tires, buckets, planters, toys, pools, birdbaths, flowerpot saucers, or trash containers. Mosquitoes lay eggs near water.
• Tightly cover water storage containers (buckets, cisterns, rain barrels) so mosquitoes cannot get inside to lay eggs.
• For containers without lids, use wire mesh with holes smaller than an adult mosquito.
• Fill tree holes to prevent them from filling with water.
• If you have a septic tank, repair cracks or gaps. Cover open vent or plumbing pipes. Use wire mesh with holes smaller than an adult mosquito.

Kill Mosquito Larvae Outside Your Home

• Use larvicides to treat large bodies of water that will not be used for drinking and cannot be covered or dumped out.
• When using larvicides, always follow label instructions.

Kill Mosquitoes Outside Your Home

• Use an outdoor adulticide to kill adult mosquitoes in areas where they rest.
• Mosquitoes rest in dark, humid areas like under patio furniture or under the carport or garage. When using insecticides, always follow label instructions.

Visit the National Pesticide Information Center at www.npic.orst.edu.