Working together, St. Charles County residents and the Division of Environmental Health and Protection can help reduce the risk of disease from mosquitoes. The division’s Mosquito Control staff has plans to monitor problem areas, test for insects, apply specific treatments when needed and educate the public on protecting themselves and others.

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“When residents take steps to protect themselves from insect bites and eliminate breeding grounds from their homes, our program is more focused and effective,” says Mosquito Control Program Manager Caroline McEwen. “With the help of our residents, we can decrease the likelihood of these disease-carrying pests in our community.”

St. Charles County’s Mosquito Control Program

The Mosquito Control program staff uses various techniques to reduce mosquitoes, including treating known breeding areas with larvicide to minimize the development of adult insects; target spraying in areas where nuisance populations have developed; and setting traps around the county to test for the presence of different species and diseases they might carry. Various species behave differently and are active at different times of the day, so knowing the types of mosquitoes in a community enables staff to apply more effective treatment.

Environmental Health contracts with several St. Charles County municipalities to control mosquito populations. Residents who live in unincorporated St. Charles County or within the city limits of Augusta, Cottleville, Dardenne Prairie, Flint Hill, Lake Saint Louis, Portage des Sioux, St. Paul, Weldon Spring, Weldon Spring Heights and Wentzville, should use the CitizenServe online portal at to request treatment. Those who wish to add their location to a “No Spray” list can call 636-949-1800.

Precautions for Residents

Individuals can assist in mosquito control by taking actions to block insect bites:

  • Use insect repellent when outdoors. Repellents containing DEET, picaridin, IR3535 or oil of lemon eucalyptus are proven to provide protection when used according to the manufacturer’s recommendations. When using sunscreen, apply it first, let dry, and then apply repellent.
  • Wear long-sleeved shirts and long pants when in a traditional mosquito habitat, like wooded areas or tall grass.
  • Drain areas around the home that may hold water for longer than five days.
  • Check screens for damage to block entry into the home.
  • Dispose of old tires or other debris from yards. 

Mosquito-Borne Diseases

While there is no evidence that COVID-19 is spread by mosquitoes, insect bites can spread other diseases to humans and pets. The two most common threats are:

  • West Nile Virus – This disease spreads when mosquitoes feed on infected birds and then transmit the virus to humans. West Nile is reported annually in virtually every state across the nation, but only approximately one out of every five people who are infected develop symptoms; such as fever, headache, body ache, vomiting and rash, and fewer than 1 percent of those infected progress into a more serious illness. For additional information on West Nile virus disease, visit
  • Heartworm – This parasite causes heart, lung and circulatory problems in dogs and cats. Heartworms enter the pet’s bloodstream through a mosquito bite and grow to maturity in blood vessels. If left untreated, the disease can be fatal. Year-round medical prevention is the best course of action. For more information on heartworm disease, please visit 

Residents with concerns about these diseases should consult a medical provider or veterinarian.