Bacteria to the Rescue by Patrick Linn, Collier Mosquito Control District

What if there was a way to reduce the number of mosquitoes in Collier County by limiting how many new mosquitoes were produced? Happily, there is a way, and here’s the best part: it’s completely natural.

By applying the insecticide Bacillus thuringiensis israelensis (Bti) to standing water, the Collier Mosquito Control District is targeting mosquitoes in their larval stage of development. That means we are essentially interrupting the lifecycle of the biters, helping us meet our mission to reduce the threat of disease and
securing the comfort of Southwest Florida residents and visitors.

The first three stages of a mosquito’s life are spent in water

A quick reminder about the lifecycle of mosquitoes: there are four stages to a mosquito’s life and the key factor to their survival is water. A female lays her eggs in or near water, which hatch into larvae, or “wigglers.” Southwest Florida’s heat and humidity allow those wigglers to mature into pupae in about a week. Then, in only a day or two, a full-fledged flying adult mosquito emerges from the pupae, resting on the surface of water until its wings are dry.

Bti is a naturally occurring bacterium found in soils around the globe. Its spores kill mosquito larvae in the water (as well as blackfly and fungus gnat larvae), but is harmless to other living things including animals, plants, fish and people. By dispersing Bti to waters known to produce abundant mosquitoes, the larvae do not mature into adults.

Larval control has become a vital component of the District’s Integrated Mosquito Management (IMM) program, and we saw a 40 percent increase in our larviciding efforts last year. Larviciding involves the application of insecticides registered with state and federal agencies. At the state level, the Florida Department of Agriculture and Consumer Services (FDACS) is tasked with ensuring compliance and regulates and licenses mosquito control programs.

District Field Technician  Nacho Barranco pours granules of Bti larvicide in a broken fountain teeming with mosquito larvae.

Surveying the waters in Collier County for larvae is a continual task for the District’s Field Technicians. From extending long handled white dippers into roadside ditches to looking for patterns of roiling mosquito larvae in larger ponds, these professionals are trained to keenly detect signs of the wigglers. During the Spring months, salt marsh mosquito larvae can even be seen in large, teeming “balls” from helicopters as they fly over coastal bays. Once detected – or anticipated – the District has numerous options to disperse the larvicides. Technicians drop Bti briquettes into storm drains, and drones are equipped to drop them into inaccessible habitat areas. Smaller areas can be treated via handheld sprayers of liquid Bti

Technicians are able to treat small areas of water with spray nozzles mounted in the front grill of their trucks. Drivers can direct the larvicide spray from inside the cab, applying it to roadside ditches, swales, retention ponds, and other small bodies of water.

 

Larger trucks are mounted with A-1 Mister and Buffalo Turbine equipment which disperse liquid Bti via an ultra-low volume aerosol mist, allowing the product to drift into inaccessible areas in residential areas. The mist is perfect for reaching the numerous containers of standing water found around homes that may be providing mosquito breeding grounds.

The District’s Buffalo Turbine truck disperses liquid Bti insecticide to control mosquito larvae in standing water.

Finally, the District’s helicopters are fitted with systems that apply Bti granules to larger swaths of land. The granules are similar in size to kitty litter, and when dissolved in water can provide up to 60 days of larval control.

Even though we can see a slight trend in decreasing adult mosquitoes as the use of larvicides increase, we are not able to disperse enough larvicide to end aerial treatments for adult mosquitoes. The very basis of Collier County’s geography ensures there is ample habitat for mosquitoes to continue breeding well beyond the reach of the District’s resources.

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

 

During the COVID-19 pandemic, our campus is closed to visitors as we strictly adhere to guidelines established by the Centers for Disease Control. However, we are available for presentations to civic groups, homeowner associations, and community groups upon request. Please contact us at 239.436.1000.

0 replies

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published. Required fields are marked *