Mosquito control materials: Q & A using facts, not fiction

By Patrick Linn, MS, MSHAPI
Executive Director, Collier Mosquito Control District

As in previous years, Southwest Florida continued to see rapid growth in 2022.  Many of our new neighbors have relocated from parts of the country where mosquito control isn’t as necessary. In this brief article, I’ll address some of the more commonly posed questions about mosquito control we receive at Collier Mosquito Control District (District), as well as provide facts to help dispel misinformation currently circulating in our community.

Q: Why do mosquitoes need to be “controlled” here?

A:  In simple terms, mosquitoes are so abundant here that they pose a significant threat to public health and comfort year-round.

With more than 50 species of mosquitoes identified and present in Collier County, the impact of not controlling mosquitoes here would exert significant negative effects on public health, tourism, and the larger economy. Some species are seasonal while others are present year-round. The District monitors five of the species very closely because of their ability to transmit diseases endemic to Southwest Florida and other subtropical climates, including dengue fever, West Nile virus, encephalitis, and yellow fever.

Q: What materials do you use to control mosquitoes?

A:  The District uses only EPA registered, approved, and regulated control materials.

The District currently uses three materials to control adult mosquitoes: Duet HD (a pyrethroid), Dibrom (active ingredient naled, an organophosphate), and Merus 3.0 (an organic pyrethroid). To control larval – or juvenile – mosquitoes in water, the District uses a number of products containing either spinosad or Bti (Bacillus thuringiensis subspecies israelensis). The labels of each material used can be found on the District’s website.

 Q: How much material is applied during one of your treatments?

A:  On a per-acre basis, the District always applies material within the label rate prescribed.

When the District applies control materials for adult, flying mosquitoes using airplanes or helicopters, the application systems are calibrated for an Ultra-Low Volume (ULV) rate. The application rate is less than 1 ounce per acre, equivalent to half a shot glass of liquid poured over an area the size of a football field.  A typical aerial treatment will treat more than 30,000 acres and take approximately two hours to complete. The material is applied from an altitude of 300’ to treat the column of air above the ground, and is almost invisible because of the extremely small droplet size. The droplets are measured at approximately 20-30 microns (e.g., one human hair is about 100 microns in size). Because of the tiny droplet size, rarely do any of the microscopic droplets make it to ground level. If they do, they dissipate quickly.

Q: Do the District’s control materials cause cancer?

A:  It is exceptionally important to understand the relative risk of exposure to the control products the District uses.

When reviewing a Material Safety Data Sheet (MSDS, aka SDS), any risks to one’s health refers to that of the handler, not the general public. It is a misconception to say that the public whom we serve would be at the same level of health risk as one directly handling the pesticide. The District always complies with label guidance and limitations. Further, our employees always comply with MSDS guidelines when handling, preparing, and/or loading materials. According to current research, residents are not in danger of contracting cancer from mosquito control materials applied infrequently and at such low amounts.  To be sure, it is very unlikely that any resident will come into direct contact at all with any of the products we use. All insecticides used in the U.S. for public health protection have been approved and registered by the EPA following careful review of data regarding their use.

Q: Will the materials affect people or pets? What if it is inhaled or if it lands on the skin?

A:  The likelihood of any direct contact with mosquito control products by our citizens and their pets/animals is very low.

Unless a person is very sensitive to or has a specific allergy to a chemical, washing the skin with soap and water after a presumed exposure is all that is needed. Given the ultra-low volume of material applied by the District, no exposure and no symptoms should be experienced.  That said, any individual concerned they may have been exposed should consult a physician at their earliest convenience.  A simple blood test will determine if any exposure has taken place.

Q: Why are treatments applied at night?

A:  The answer is two-fold:  That’s when mosquitoes are most active and the atmosphere is most conducive to treatment.

Have you noticed most mosquitoes aren’t as active during daylight hours? Their activity is heightened from dusk to dawn, so applying adulticide treatments after sunset is the most effective time to “knock down” the mosquitoes. Another important reason for nighttime applications is to avoid affecting the pollinators not active at night, including bees, dragonflies, and butterflies.

Normally, the District offers public tours of our facilities to learn more about our operations, but Hurricane Ian delivered nearly three feet of storm surge through our campus. All buildings are in a state of restoration and are not habitable, which is the primary reason the District is building a hangar at the Immokalee airport – a safe haven during storms to ensure uninterrupted service to our community. However, our Outreach team conducts presentations at group meetings. ease call our office at (239)436-1000 to request a presentation or if we can provide more information.

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