With the rain, come the mosquitoes

Mosquito-laying-eggs

The Lee County Mosquito Control District is hard at work, doing multiple flights each day and night to reduce the numbers of adult mosquitos and to prevent larvae from developing into the adults that can spread disease.

The first line of defense against mosquitos is prevention. Any pool of standing water is a potential breeding ground for the pests.

Shelly Redovan, Deputy Director of Education and Communication for the Lee County Mosquito Control District, has a few tips that can help reduce the number of mosquitos around your home.

“Flush bird baths or any containers holding water every three to four days,” she advised. “If you grow bromeliads, flush them every three to four days. Turn any receptacles that can hold water upside down. Keep your gutters clean. If you have a pond, keep minnows in it, and if you have a rain barrel, cover any openings with screen to keep mosquitoes from laying their eggs inside.”

On a larger scale, LCMCD maintains rain gauges around the island. The inspector for Boca Grande checks the gauges regularly and keeps a close watch on tides. If treatment is needed, it can be provided from two directions, from the ground using sprayer trucks or from the air using planes and helicopter.

“If either rain or tide leads to standing water, the inspector will check for developing larvae,” explained Redovan. “The inspector will do this by truck in areas accessible by roads and by helicopter for areas not accessible by roads. If they find mosquito larvae, the water will be treated by truck or helicopter.”

If the district is unable to treat the larvae before they develop into adult mosquitoes and surveillance indicates the need to adulticide, or treat for adult mosquitoes, the district will use many of the same methods to control the adults.

“The district uses surveillance to monitor the level of adult mosquitoes throughout the county,” said Redovan. “We have trap trucks, Center for Disease Control light traps, a sentinel chicken flock and we track landing rate counts to monitor the level of the adult mosquito population in Boca Grande. If the surveillance shows an increase in the number of adult mosquitoes or a health threat, we will treat the adult mosquitoes.”

When treatment is done for adult mosquitos, it is done at night when they are most active and when other flying insects are not as active.

There are three main methods used to treat larvae in Lee County – Bti (or Bacillus thuringiensis israelensis), methoprene and temephos. BTI are bacteria that the mosquito larvae eat. BTI are deadly only to very specific insects, so other larvae growing in the water are unaffected. Methoprene is a chemical that mimics the hormones of insects. Rather than poisoning the larvae, it actually prevents them from maturing into an adult. Temephos is an organophosphate that affects the central nervous system of the larvae, killing them.

All three are dispersed into a fine mist, and in the case of BTI, there is no risk to humans or animals. The other two agents are used in such small amounts that the risks to humans or animals are all but non-existant. The primary aerial adulticidal material used by the mosquito control is Naled, another organophosphate. All insecticides used in Florida must first be approved by the U.S. Environmental Protection Agency, then by the Florida Department of Agriculture and Consumer Services.

The FDACS states on their website that, “The USEPA recently conducted preliminary risk assessments for Naled. These assessments calculated risks under a number of different scenarios, including assumptions of several Naled spraying events over a period of weeks and toddlers ingesting some Naled in soil and grass along with exposure through skin and inhalation exposure. Because of the very small amount of active ingredient released per acre of ground, the USEPA found that for all scenarios considered, exposures were hundreds or even thousands of times below an amount that might pose a health concern.”

How often spraying occurs depends on several factors.

“There is no schedule,” Redovan explained. “Our work depends on standing water. Everything is based on scientific documentation of need. In April we started having more frequent events triggering larvicide activity."

The most recent “event” was Tropical Storm Debby, which soaked the island with rain for days.

“Tropical Storm Debby brought over two inches of rain county-wide,” said Redovan. “More importantly for Boca Grande, it pushed high tide inland for several days. The winds from Tropical Storm Debby prevented the district from larviciding from June 23 to the 28. This lack of larviciding created a need to do more adulticiding over most of the county.”

The type of mosquito encountered on Gasparilla Island, the salt marsh mosquito, develops from egg to adult in five days. The winds of Tropical Storm Debby kept the mosquito control air fleet grounded for almost a full week, so an entire generation of eggs had time to mature to adulthood.

Now the department is hard at work catching up. If you have any questions, or need to request treatment in your area, you can contact the LCMCD at (239) 694-2174 or go to their website, lcmcd.org.