Since the mosquito that carries Zika is most active at predawn and at sunset, all spraying must take place at those times.
So far, there have been 56 local transmissions of the Zika virus in Florida
, which has 20.6 million residents. The state has seen 596 travel-related cases of Zika, according to the Centers for Disease Control and Prevention (CDC).
Health officials have sprayed pesticide and larvicide on the ground in areas where they believe the mosquitoes may be, and are expanding those efforts with the aerial use of naled.
The spraying was originally scheduled for Thursday, but was delayed for a day after concerned residents protested.
Andres Blanco wasn't among those protesting. A valet at South Beach's landmark Clevelander Hotel, Blanco said he wasn't scared.
"No way man, I think it's good!" The longtime Miami Beach resident said. "They've got to do something to kill those mosquitoes."
Naled used since 1950s
Experts say there's no reason to be concerned over the effects of the insecticide
on human health and the environment. The amount of insecticide used is minimal -- two tablespoons per acre -- about the size of a football field, according to the CDC.
"Aerial spraying using Naled and other insecticides has been used in many populated areas of the continental United States, including Miami, Tampa and New Orleans to help control mosquitoes," the CDC said on its website
The European Union, however, bans the the use of naled, calling it "a potential and unacceptable risk"
to human health and the environment.
South Beach resident Peter Beach, 62, said he is really angry about the spraying. Beach, who described himself as a closet anarchist, voiced contempt for the EPA and CDC approval of naled, the main chemical in the insecticide Dibrom.
"This is a toxic substance that kills everything," he said. "You think these tourists on the beach know they are lying on sand that was hit with a toxic carcinogenic hours earlier? No way."
The US has used naled since the 1950s,
and sprays it on about 16 million acres nationwide annually. Health officials use it to prevent mosquitoes after disasters such as hurricanes and floods, according to the CDC.
Naled breaks down swiftly in water and sunlight, and its chemicals don't cause health problems in people or pets if used in small quantities, according to the CDC.
Sprayers produce fine droplets that are small enough to stay airborne and intercept mosquitoes in flight. It kills mosquitoes on contact.
But while US health officials say it's safe, Europe has banned the use of agricultural products containing naled over safety concerns.
Tristan Mullings, 27, was visiting from Brooklyn. He was aware of the Zika outbreak before he came -- "I can't let no mosquito ruin my vacation" -- but unaware they would be spraying Friday morning. He voiced concern when he learned the chemicals had been linked by some to neurological disorders
"Then I think the spraying is worse (than Zika)," he said.
Janet McDonald, an English teacher in Mexico who was in Miami vacationing with a friend from Canada, said spraying was worth the risk compared to the risks posed by a mosquito-born disease.
"Am I scared?" said McDonald, referring to naled. "No, I've had Dengue fever, that is scary."
The presence of Zika-carrying mosquitoes in Florida has sparked fears, especially after Gov. Rick Scott announced in July that the first local transmission of the virus in the continental United States
occurred north of downtown Miami.
A few days later, in an unprecedented move, the CDC announced a travel warning, advising pregnant women not to visit that area. Authorities launched aggressive mosquito-control measures, including spraying in the area.
Last month, the CDC advised pregnant women not to travel to an area of Miami Beach limited to 1½ square miles.
Pregnant women are at greatest risk because the virus can have devastating consequences for an unborn baby, including the birth defect microcephaly and other neurological disorders, as well as miscarriage and stillbirth among women infected while pregnant.
In addition to human health, critics say naled kills pollinators and wildlife, and is toxic to the environment.
South Carolina beekeeper Juanita Stanley recently lost more than 3 million bees
when Summerville officials aerially sprayed a small area of the town for Zika-carrying mosquitoes.
"In the summertime, the bees are already out at dawn, when aerial spraying is recommended," said entomologist Jeffrey Harris, who runs the Honey Bee Extension and Research Program for Mississippi State University. "So spraying in the morning is the worst thing they can do for bees."