Outbreak Of Coastal Mosquitoes Appears In Rural Sarasota: County

SARASOTA COUNTY, FL — A recent mysterious outbreak of coastal mosquitoes has been solved, Sarasota County Mosquito Management said on its website.

In early January, the department received reports of massive numbers of coastal mosquitoes (Aedes sollicitans) appearing 20 miles from their usual habitat. Their breeding habitats are usually salty tidepools and cordgrass along South Florida beaches.

“And, while it’s not uncommon for these mosquitoes to migrate long distances, the extremely high concentration of sollicitans in the area indicated that a rather monstrous hatch-off had occurred from a very nearby breeding source,” SCMM said. “But how?”

While Sarasota County beaches like Siesta Key are used to large numbers of these aggressive mosquitoes, which the SCMM monitor rigorously, they’re not found in rural areas.

“In rural Sarasota, however, where there are no beaches or tidepools, the Aedes sollicitans mosquito can only exist in transience, passing through the area in a hopeless hunt for a habitat in which to lay her eggs; something she should not be able to find,” according to the SCMM website. “Yet, against all logic, Aedes sollicitans were somehow breeding in egregious numbers in rural Sarasota.”

Sarasota County Mosquito Management technicians set out to find their breeding source in this non-coastal area. They inspected numerous locations by foot and vehicle, stopping at the county line after they couldn’t find the mosquitoes’ habitat, SCMM said.

They sprayed insecticide to reduce the number of adult mosquitoes in the area, hoping the outbreak was an anomaly. Technicians continued to monitor the area, though, and eventually saw the numbers start to increase again.

Suspecting the mosquitoes’ breeding source could be nearby in Manatee County, SCMM manager Wade Brennan reached out to the Manatee County Mosquito Control District for help.

The two agencies worked together to locate the breeding ground for the pest on farmland in Manatee County just over the border.

“It seems that a farming technique used to restore grazing lands led to the creation of an artificial saltwater habitat which Aedes sollicitans turned into a rural breeding ground. The farming technique, which involves applying salt and fertilizer to a field of vegetation, then flooding the soil with water for five days, can produce a habitat that mimics the coastal environment sollicitans are used to,” SCMM said. “Migrating female sollicitans that happen upon this salty oasis will be compelled to deposit their eggs among the grass and near the water. Rain or irrigation will then submerge the eggs or flush them into the water where mosquito larvae will hatch within a day or two. Approximately one week later, adult mosquitoes will emerge.”

This cycle continues when female mosquitoes born in that rural setting return to the same habitat to lay their own eggs, SCMM said.

At the end of February, the Manatee County Mosquito Control District treated the habitat by aerial spraying to control the swarms of mosquitoes. SCMM also sprayed in Sarasota County again Friday to control the adult mosquitoes on that side of the county line. They’ll continue to monitor the area.

"What's most evident in studying this case is that mosquitoes are vicious, adaptable and alarmingly prolific," SCMM said. "To be sure, the war against these tiny assassins requires neighbors (and neighboring mosquito control agencies) to work together if we ever hope to successfully 'fight the bite.'"