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1. What is the primary goal of the mosquito control program?

The goal of the St. Charles County Division of Environmental Health and Protection's mosquito control program is to decrease the number of disease-carrying pests that cause a nuisance to the general population. We target breeding sites that harbor larvae and spray during evening hours for flying adult mosquitoes. In addition, we educate residents on the importance of eliminating potential breeding sites around their community.

2. What method does St. Charles County use to treat mosquitoes?

There are many products that control mosquitoes, with varying levels of effectiveness and impact on the environment. The primary treatments that the Division of Environmental Health and Protection employs are Kontrol 4-4 for adult insects and Aquabac 200G for larvae.

3. How is Kontrol 4-4 used in mosquito control?

A mosquito goes through four distinct stages during its life cycle: egg, larva, pupa and adult (imago). Kontrol 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. 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 square feet — so even though spraying may be done from the street; it is designed to reach backyard areas. St. Charles County began using Kontrol 4-4 for insect treatment in 2019.

4. What is Aquabac 200G, and how is it used in mosquito control?

In addition to removing adult insects, another mode of mosquito control is the eradication of larvae. After determining that standing water is contaminated with mosquito larvae, Division of Environmental Health and Protection staff uses Aquabac 200G to inhibit development. Aquabac 200G is crushed corn cobs treated with bacteria that eat away the stomach and intestines of the larvae before they further develop into pupae and adults. Although very effective on the mosquito larvae, this process causes no harm to people, animals or other organisms.

5. Does Kontrol 4-4 pose a risk to human health?

With any pesticide or chemical application, caution must be exercised in accordance with the manufacturer's suggestions to ensure safety. St. Charles County employs certified public pesticide applicators that are trained by the Missouri Department of Agriculture. The chemicals we apply are carefully diluted, and our machines are calibrated daily to ensure the most effective distribution of pesticide during our control efforts, with no risk to the public. When truck drivers pass residents, they turn off the spray apparatus. While the generator may still be running, the sprayer does not disperse chemicals near people.

6. What can I do as a resident to help control mosquitoes in my community?

The best way to cut down on mosquitoes is through water management. If you have any standing water on your property, you can limit habitat and breeding areas by filling in low spots that hold water or by observing proper drainage management. A common breeding area in many yards is in buckets, unused tires, gutters, bird baths, trash piles or other objects that can hold water for a week or longer. Additionally, if you have a lake or pond on your property, a common tool to limit mosquito growth is the use of a fountain or water agitator.

Adult mosquito application by Division of Environmental Health and Protection staff is a complaint-based process — meaning we only spray when residents alert us that mosquitoes are a problem in their neighborhood. Please call our office at 636-949-1800 or complete this online form to alert us to potential problems. A common question that you may be asked after this complaint is "Are the mosquitoes biting?" While this may seem to be a strange question, by asking it our staff can best predict when to spray in your area. Only female mosquitoes bite, and it may take up to two extra days for females to emerge versus male mosquitoes.

To protect yourself while outside, please apply a mosquito repellent containing DEET, picaridin, IR 3535 or oil of lemon eucalyptus.