By:
Tom

Source(s):
Jonathan Day jfda@ifas.ufl.edu, (772) 778-7200 ext. 132
Roxanne Rutledge crr@ifas.ufl.edu, (772) 778-7200 ext. 172
Jonas Stewart jstewart@co.volusia.fl.us, (386) 239-5616

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VERO BEACH, Fla. — Tiny, blood-sucking flies that plague Florida’s coastline should be less common this fall, thanks to summer rains that flooded areas where the pests breed, says a University of Florida expert.

Biting midges, also known as no-see-ums, are a constant presence during warm weather but appear in greater numbers during October and November, and again in April and May, said Jonathan Day, an entomologist with UF’s Institute of Food and Agricultural Sciences. The fall population boom follows peak high tides that flood salt marshes and hatch dormant eggs stockpiled throughout the summer months.

This year, summer rainfall left standing water in many low-lying coastal areas, making potential egg-laying sites inaccessible, he said. Biting midges lay eggs in muddy soil but cannot deposit them on top of standing water.

“Their loss is our gain, so to speak,” Day said. “Biting midges aren’t going to disappear altogether this fall, but if you’re on the coast you’ll probably get fewer bites compared with years when we had a dry summer.”

Two coastal biting midge species are affected by the situation — Culicoides furens, which is found along the coast throughout the state, and Culicoides barbosai, found in coastal marshes primarily in South Florida, said Day, who studies biting insects at UF’s Florida Medical Entomology Laboratory in Vero Beach.

Populations of inland biting midge species will probably be reduced as well, he said. Though less prominent than their coastal cousins, inland biting midges are found near lakes, swamps, lowland marshes and livestock pastures.

Florida is home to about 50 species of biting midges, but only a handful are significant human pests, said Roxanne Rutledge, another entomologist at the UF laboratory. Rutledge recently wrote a profile on the biting midges of Florida, which can be found online at http://creatures.ifas.ufl.edu/aquatic/biting_midges.htm.

Adult females feed on blood to obtain nutrients they need to produce eggs, and their bites cause a sharp, burning pain, she said. Because the midges measure less than one-eighth of an inch long, they are seldom seen by their human hosts.

“The bites can be very annoying, but in the United States there are no human diseases caused by the biting midges,” Rutledge said. “Some people do have a mild allergic reaction and experience welts and itching for a couple of days.”

Despite the temporary population decline this fall, people going outdoors in biting midge habitat should take basic precautions against the pests, she said.

“Wear long-sleeved shirts and long pants if possible, and use a repellent containing DEET on your exposed skin,” Rutledge said. “Try to avoid outdoor activity at dawn and dusk, especially if the air is still.”

Biting midges are weak fliers, so homeowners can blow the pests away from patios and decks with large electric fans, she said. Screened-in pools and porches may need to be protected with fans as well, because biting midges can pass through most wire mesh.

Unfortunately, little can be done to control the pests on a large scale, Rutledge said. No community in Florida, or any other state, has a biting-midge control program.

“The biggest problem is, there’s no option for destroying the larvae in a way that’s economical, efficient and environmentally sound,” she said.

Because biting midges lay their eggs in muddy soil, vast areas can be used for breeding, Rutledge said. Locating eggs or larvae requires close examination of soil samples, which takes time. Even if larvae are located, there are no safe, approved insecticides that can penetrate the mud to reach them.

“For now, the biting midges have the upper hand, and we just have to rely on low- tech solutions,” she said.

The lack of large-scale control options can be frustrating to the public, and to public-health officials, said Jonas Stewart, director of the Volusia County mosquito control program in Daytona Beach.

“We get calls from citizens asking for help with biting midges, and the only thing we can do is spray for the adults, which only works temporarily,” Stewart said. “People sometimes assume that controlling biting midges is as easy as controlling mosquitoes and, unfortunately, it’s not.”

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