Voters in one Florida county were at odds on a ballot referendum Tuesday about whether to allow the first trial of “Frankenflies” — mosquitoes genetically engineered to reduce populations of the species that spreads Zika.

That species, the Aedes aegypti, lives in homes and is difficult to root out with insecticides. In addition to Zika, they spread yellow fever, dengue and chikungunya.

In Key Haven, the town where the trial could be staged, more than 65 percent of voters rejected the plan. In Monroe County, which encompasses Key Haven, more than 57 percent of voters said yes to it.

The ballot measure, sometimes referred to as a “straw poll,” is non-binding. A final decision on the question will be made by the Florida Keys Mosquito Control District Board, which is scheduled to meet Nov. 19 to discuss the poll results as well as the results of five other surveys the county has conducted.

The outcome of these deliberations could encourage further exploration of the technology, which its manufacturer and charity benefactors describe as a silver bullet to curbing mosquito-borne illnesses, but detractors say is an expensive and risky business opportunity.

“While we did not win over every community in the Keys, Oxitec appreciates the support received from the community and is prepared to take the next steps with the Florida Keys Mosquito Control Board,” said CEO Hadyn Parry in a statement. Oxitec, the company that developed the “Frankenflies,” is owned by Intrexon Corporation, a biotechnology firm with a portfolio focused on synthetic biology.

If the trial moves forward, the British-based company’s mosquitoes would be released three times a week over the small peninsula. Key Haven is home to just 1,000 residences and a single gas station. The native mosquito population is insulated by seawater and the island’s main highway, making for a perfect trial location, the company said.

If the trial goes as planned, those mosquitoes will breed with native females, the ones that bite. Both the genetically engineered insects and their offspring carry a fatal gene, and die quickly. Over time, the population will thin out.

“We’re very happy with the results,” Mosquito Control Board Chairman Phil Goodman said of the Monroe County vote. He thought Key Haven voters got bad information about the safety of the trial and anticipates the board will choose to go forward, but find another site in the county.

But the referendum has implications beyond this tiny section of the Florida Keys. Miami-Dade County, Florida’s most populous county, has been watching closely and is considering using the genetically modified mosquitoes as well. But the small enclave of Key Haven is a vastly different place than the bustling tourist destination of Miami-Dade, home to 2.7 million people.

A company representative said he could not discuss pricing until the product is sold commercially — as opposed to in a trial period. But in the past, Oxitec has charged based on number of people benefiting from the technology’s use. In Brazil, the tab ran $7.50 per resident. Company officials, however, have told Monroe County that its costs will not be more than it already budgets to control Aedes in the lower keys — about $1.2 million annually, Goodman said.

Trial skeptics raise additional red flags. For instance, since the genetically engineered mosquitoes do not by design produce offspring, the company would have to continually pump them into the environment.

“If you want to implement a male sterilization program, there are other ways to do that,” said Durland Fish, a Yale University professor of microbial diseases as well as forestry and environmental studies, who questions the plan. “This is a business opportunity. This is expensive. And you can’t stop doing it.”

Some vocal Monroe residents have raised environmental concerns and even circulated an online petition.

The Food and Drug Administration determined in August that the trial would have “no significant impact” on the environment, paving the way for the mosquitoes’ release. And the World Health Organization and Pan American Health Organization have tentatively recommended expanding trials, with the caveat that more clinical data is needed.

But it may not be so straightforward, said Fish. Eliminating Aedes from one ecosystem could lead to a reinvasion, or an invasion of another disease-carrying species, like Aedes albopictus, he added.

Luke Alphey, who engineered the mosquitoes and cofounded Oxitec, has a very different view. “Part of the motivation for this research was using modern genetics to provide the striking benefits of this kind of approach [sterilizing mosquitoes],” including the avoidance of insecticides and being able to target a specific species without harming others.