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War against mosquitoes is underway in Florida after Hurricane Ian


First, the storm. Then, a plague of insects. 

Hordes of mosquitoes have proliferated in floodwater and debris left in Hurricane Ian’s wake, and now swarm Florida communities. 

State and local officials are waging a multimillion-dollar war against the bloodsucking insects — which are known to spread diseases like West Nile virus and St. Louis encephalitis  — as they try to keep residents safe and prevent the voracious insects from slowing down the recovery crews working to fix power lines and rebuild infrastructure. 

“The mosquitoes are out there, and they’re biting,” said Eric Jackson, the deputy director of the Lee County Mosquito Control Division. “It is just a constant effort to knock down as many of those flying, adult mosquitoes as fast as we can.” 

After the initial devastation from a hurricane or flood, other threats follow, including bacterial infections, respiratory diseases and illnesses spread by pests that proliferate in standing water. Mosquitoes are an expected, annoying and sometimes dangerous secondary consequence of a storm, one that can hinder rebuilding and raise the risk of an outbreak if left uncontrolled. 

“Imagine a couple thousand coming at you. That’s the big concern after hurricanes and large flooding events,” said Daniel Markowski, a technical adviser for the American Mosquito Control Association. “The sheer number of mosquitoes can make any daily life activity horrendous.”

Researchers expect these challenges to arise more often in the future, since climate change is raising the risk of more intense hurricanes, heat and flooding, as well as creating conditions that are more conducive to mosquito development and their incubation of viruses.

Mosquito control in Florida is about as sophisticated as it gets in the United States. The Lee County Mosquito Control District, a special district in one of the communities hit hardest by Ian, employs about 100 workers, Jackson said. It has five helicopters, six planes and 12 trucks that carry out aerial and ground spraying missions to reduce mosquito populations with pesticides. 

Laboratory workers regularly test blood collected from caged “sentinel chickens” living at 17 sites within the county, so officials will know if the chickens are getting bitten and becoming infected with viruses spread by mosquitoes. Crews also monitor mosquito traps year-round to understand if and where populations are taking off. Workers sometimes even track “landing rates” by counting how many mosquitoes alight on them — and sometimes bite — in one minute’s time.  

A researcher examines mosquitos under a microscope in a lab.
Anne Askew, a biologist in the Lee County Mosquito Control District’s Larviciding Department, uses a microscope to identify mosquito species.
Lee County Mosquito Control District

In Lee County, where Fort Myers is located, mosquito counts in the traps began to spike about a week after Ian. 

Whereas the county’s traps captured nearly 34,000 mosquitoes in all of October 2021, the same traps had already collected more than 107,000 in the first 12 days of this month. Residents and businesses made nearly 600 calls to the district requesting mosquito treatment during the first half of October. 

Other Florida counties reported even sharper increases. 

Last week in Brevard County, on Florida’s east coast, traps collected at least 22 times the area’s weekly baseline mosquito count, according to data reported to the Florida Department of Agriculture and Consumer Services. The county, northeast of Lee, was in the path of Ian after the hurricane weakened post-landfall. Nearby Seminole County, northeast of Orlando, counted about 46 times its normal level of mosquitoes.

More than 30,000 mosquitoes lay in a trap
More than 30,000 mosquitoes were trapped and collected in 17 hours earlier this week in Brevard County, Fla. Traps, which are baited with carbon dioxide, provide surveillance and data to officials.Florida Department of Agriculture and Consumer Services

Mosquito control professionals know the sequence of events to expect after a major storm. 

“The larvae are going to emerge in a week roughly,” Markowksi said.

So in the initial days, crews focus on disseminating larvicides: treatments toxic to mosquito larvae. These substances include bacteria, oils and chemicals that halt insect growth, and are often dropped from a helicopter or applied by crews on the ground. 

But flooding often limits the crews’ access. There’s too much water and not enough time. 

The first mosquitoes to emerge after a storm are the aptly named floodwater mosquitoes. 

“Every mosquito habitat has eggs laying in the soil, waiting for this rain, [it] gets flooded and you have literally millions upon millions emerging at once,” Markowski said. 

A truck sprays larvicide into a ditch
A crew sprays liquid larvicide from a truck in Lee County, Florida, to kill mosquito larvae before they can transform into adults. Lee County Mosquito Control District

That’s when control crews switch to spreading pesticides. Pilots spray small droplets that kill the insects on contact. 

In Lee County, these operations often happen during the night, when some mosquitoes are most active. The pilots wear night vision goggles and follow a computer-guided system. Sometimes, three aircraft fly in a single evening. They typically travel 300 feet off the ground at speeds of between 170 to 340 miles per hour.

“It’s definitely not an entry level job,” said Thurbie Botterill, the district’s chief pilot.

As flooding recedes, some water remains and begins to stagnate. That’s when culex mosquitoes — which Markowksi calls the most “worrisome” because they are responsible for transmitting West Nile fever and St. Louis encephalitis — begin to come out. 

Container mosquitoes known to transmit dengue fever and other viruses are another worry. 

“An old soup can in the woods or an old tire, every container has water now,” Markowski said. “You can have these [container] mosquitoes become quite prevalent and a big problem.”

This year, 30 cases of locally acquired dengue fever and two cases of West Nile virus had been reported to the Florida Health Department by Oct.15, according to a surveillance report. Last year, Florida reported no locally acquired cases of dengue and five West Nile cases.

Dengue fever was considered eliminated in Florida from 1934 to 2009. But in 2020, the state saw simultaneous outbreaks of dengue and West Nile, with 71 cases of locally acquired dengue and 86 cases of West Nile.

This year, Florida has also seen an increase in flesh-eating bacterial infections. In the aftermath of Ian, Lee County Health officials warned residents that standing water after the hurricane could enhance that threat

Pesticide spraying operations are currently in full swing in Lee County and other places in the state. 

The pesticides commonly used for aerial spraying are registered with the Environmental Protection Agency, which recently reviewed the use of one of the most common, called naled. The agency found that it could pose some risk to children in high doses, but that the spray dissipates quickly and is often used in very small amounts. The agency recommends that children avoid playing outside for four hours after aerial spraying, that people keep their windows closed during spraying and that the public be notified ahead of time.

Already since the hurricane, the district has treated more than 550,000 acres and conducted 21 aerial missions. 

Twelve other counties with less mosquito-control resources than Lee have requested assistance from Florida’s agriculture department. Through those efforts, more than 1.2 million acres have been treated so far, with more treatments planned. 

The state pays its two contractors slightly more than $2.30 per acre for this work, meaning the state bill is already nearing $3 million for treatments. 

Thus far, Florida hasn’t requested any federal assistance for mosquito control, as Texas did after Hurricane Harvey in 2017, when the U.S. Air Force sprayed nearly 7 million acres for mosquitoes

Florida officials don’t think federal help will be necessary, though Hurricane Ian’s damage has created challenges for mosquito control workers. 

The storm damaged the Lee County Mosquito Control District’s airfield, but it was still able to get planes up in the days after landfall. Initially, pilots helped state, county and federal officials with damage surveillance and assessments by air, before beginning work on mosquitoes.

Ian’s destruction has also scrambled the pilots’ perspectives. Obstacles like power lines that are ingrained in memory were suddenly masked or obscured by debris or new patterns on the ground. New hazards to low-flying aircraft, like temporary cell phone towers, now dot the landscape.

“It’s overwhelming. … It’s got none of the same canopy at all. All the trees look dead,” Botterrill said. “The environment has got its own, new risks.”



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