MIAMI BEACH, Fla. — Backlash over aerial spraying of the insecticide naled in South Beach is prompting residents elsewhere in Florida to question how it’s used in local mosquito control operations.

Miami-Dade County plans another spraying of the pesticide early Sunday over South Beach, the first place on the U.S. mainland where the Zika virus was isolated in mosquito samples.

The first round of aerial spraying over a 1.5-square-mile area in Miami Beach was completed early Friday. According to The Miami Herald (http://hrld.us/2cL57UF ), while the plane could be seen and heard, the fine mist of pesticides being sprayed to kill adult mosquitoes could not be seen, smelled or felt by reporters on the ground.

The operation had been delayed for one day after some Miami Beach residents and elected officials protested the county’s use of naled, saying they’re concerned that exposure to the pesticide can cause health problems in people. State, county and federal officials have said the minuscule amounts sprayed at dawn and dusk would not harm people.

Bill Louda, a professor of chemistry and biochemistry at Florida Atlantic University, said researchers have found that naled can be harmful in large doses, but not in the small quantity — approximately two tablespoons per acre — used in aerial spraying.

Until an adequate alternative is developed, “we must balance risk versus benefit and not go overboard with the fearmongers,” Louda told The Palm Beach Post (http://pbpo.st/2ctSBau ).

Naled has been used in the U.S. since 1959. Palm Beach County has used it for many years to eliminate nuisance mosquitoes, including an Aug. 23 spraying from a helicopter over 162,000 acres that border the Everglades, mosquito control officials said.

Some residents have raised concerns about the chemical, said Gary Goode, environmental program supervisor for Palm Beach County’s mosquito control.

“We rely on the expertise for the use of these materials on those regulatory agencies like the EPA to assure that they’re not materials that are going cause any undue harm to our population,” Goode said. “We don’t have the funding to make those determinations ourselves.”

The Naples Daily News reports (http://bit.ly/2cOsM5z ) that the Collier Mosquito Control District has been receiving an increasing number of calls from residents who want the southwest Florida county to stop using naled.

The district, which has used naled for 22 years, rescheduled its evening spraying to 10 p.m. after school started because children and families are outside for sports, said Mark Clifton, research entomologist at the district.

“It does get us out of the way of people,” Clifton said.

The district recently upgraded its laboratory testing capabilities to test mosquitoes for Zika and other viruses, such as dengue fever. None of the 150 batches of mosquitoes trapped for testing so far — with 20 to 30 mosquitoes in each batch — have tested positive for the virus, Clifton said.

Puerto Rico’s governor wouldn’t authorize naled’s use because of environmental concerns, despite widespread Zika infections there. Miami-Dade County has scheduled two more aerial spraying flights for Miami Beach for the next two weekends.

Different pesticides targeting mosquito larvae are being spraying on the ground from trucks and by hand. The county previously performed aerial spraying over Miami’s Wynwood arts district, where health officials confirmed the first Zika infections acquired from mosquitoes in the continental U.S.