Mosquito Control

A team effort between residents and the St. Charles County Mosquito Control program can help to "Block the Bite" and reduce the risk for exposure to insect bites and illnesses that nuisance insects may spread.

The St. Charles County Mosquito Control Program's major objectives are to:

  • Solicit public participation in reducing the health risk associated with disease-carrying insects through education and action.
  • Provide information and encouragement to eliminate potential breeding sites around home settings.
  • Identify and record potential and historical mosquito breeding sites located in St. Charles County.
  • Monitor breeding sites within St. Charles County and apply appropriate treatment to these areas as needed.

Efforts by Residents

Use Repellent to Discourage Biting

The best way to discourage insect bites is to take preventative action before going outdoors and when returning home. Here are a few simple precautions to minimize exposure to insect bites:

  • Use insect repellent containing DEET, picaridin, IR355 or oil of lemon eucalyptus when outdoors. Remember to apply sunscreen first, allow it to dry, and then use insect repellent.
  • Wear light-colored, loose-fitting clothing. When traveling in areas known for ticks, mosquitoes or other insects, including tall grass and wet or wooded settings, wear long sleeves and long pants.
  • Brush clothing and check for insects after being outside. Check pets as well.

Diminish Development Around Your Home

Although discouraging insect bites is effective, diminishing populations before they develop provides more protection than any other methods. Proper maintenance of your property is the first step, as mosquitoes can develop from eggs into adults within 7-14 days, when conditions are favorable. Here are additional methods for diminishing mosquito breeding areas around your home:

  • Fill or drain areas where water may collect for more than one week.
  • Flatten cans and containers or puncture holes in bottom.
  • Completely seal cesspools and screen all vents.
  • Clean clogged roof gutters and drain flat roofs so no water stays.
  • Cover all standing receptacles, such as rain barrels in rural areas, with netting.
  • Empty and refill outdoor bird baths every few days.
  • Stock garden pools and ponds with small fish or aerate them.
  • Tilt wheelbarrows and machines with containers to prevent holding water.
  • Empty watering cans and wading pools after using.
  • Dispose of old tires or any debris that holds water.

Efforts by St. Charles County Mosquito Control


Treatment Activity


The Division of Environmental Health and Protection controls mosquitoes by monitoring or eliminating breeding sites and by applying treatment to nuisance populations. Staff uses two techniques for various stages of development:
  • Injecting larvicide into pools of standing water to prevent development.
  • Dispersing treatment at targeted areas to reduce adult populations.
St. Charles County residents, who live in our treatment zones and are concerned about nuisance mosquitoes, are encouraged to use our online form or call 636-949-1800 to request assistance.

Collection and Assessment



To study the local population, the division traps mosquitoes at various locations around St. Charles County and examines them to establish the commonly found species. Confirming the types of mosquitoes in our community enables staff to better treat populations, as various species behave differently and are active at different times of the day. Additionally, this collection allows staff to test individual insects for the presence of disease.

Annual Activity Report



In addition to responding to citizen requests, we also monitor mosquito activity throughout the traditional season. 
Please review our report on mosquito control activity during the most recent season and for activity in previous years.