UF Researcher's Innovative Fence Helps Control Sand Flies

June 24, 1998

BOYNTON BEACH, Fla.--When the children at St. Mark Catholic School hit the playground, the biting sand flies in the mangrove marsh next door start smacking their little bloodsucking lips.

Like all their biting kin--mosquitoes, deer flies, horseflies and black flies--sand flies use carbon dioxide to locate a host. So the huffing, puffing children on the playground present a smorgasbord, said University of Florida researcher Jonathan Day.

"They are all beacons out there, flashing 'blood meal, blood meal, blood meal,'" said Day, an entomologist with UF's Institute of Food and Agricultural Sciences.

But Day hopes to use the sand flies' thirst for blood against them. Between the marsh and the playground he has built a fence that seeps carbon dioxide. By simulating a human presence, the carbon dioxide tricks the sand flies into making a detour and lures them into traps along the fence line. The date with dinner becomes a date with death.

The carbon dioxide fence at the school is the first field demonstration of Day's system. A test of a similar fence at UF's Florida Medical Entomology Laboratory in Vero Beach caught 200,000 sand flies per night. Already, he said, the real-world test looks promising, and parents of students at St. Mark agree.

"My kids would come home with terrible bites all over their bodies, almost as bad as chicken pox," said Carol DeCanio, whose son and daughter attend the school. "It was very difficult sending the kids to school knowing they would come home with these bites."

Since Day turned the fence on in April, however, her son Michael says things have gotten better.

"It used to itch so much I couldn't stop itching," Michael said. "This helps because in the middle of class you're not itching anymore. You're doing your work instead of scratching your bites."

Repellents provide limited relief because sand flies are so persistent, Day said. With populations in the millions near swampy areas, it is inevitable that some sand flies will find little patches of skin not treated with repellent and even crawl up under hair.

"Their bite is very painful," Day said. "They really can make life unbearable, sometimes."

Day says future applications of the carbon dioxide fence range from small-scale use by homeowners to large-scale use to large-scale settings such as sports fields and resorts. In the Caribbean, particularly, he says sand flies are "unbelievable," even spreading certain livestock diseases and preventing recreational use of some islands.

The system would be easy to adapt.

The fence is a lattice of PVC pipe, hung with mesh panels coated with mineral oil. The pipes carry carbon dioxide and octenol, a chemical that sand flies mistake for water buffalo breath, which they relish.

Day says the panels act as "centralized killing stations." The carbon dioxide/octenol brew draws the flies to the fence, where they get trapped in the mineral oil on the panels and die.

To evaluate how deadly the fence is, Day places traps inside the fence on the playground. The playground traps consistently have a lower sand fly count. Day also turns the fence off periodically to do bite counts, which always go up when the fence is not operating. Day said he hopes for a long-term impact on the overall sand fly population after the fence has been running for months or even years.

Sand flies infest all of coastal Florida. Day said many control strategies have been tried against sand flies, also known as no-see-ums and winged teeth, but all have failed because of the insects' complex biology.

The carbon dioxide fence grew out of a 14-year research project to develop environmentally friendly techniques of trapping sand flies. Mineral oil works beautifully because it is non-toxic and the sand flies are not strong enough to fly out of it.

"Historically, we'd treat a marsh like this one near the school with DDT, and that worked great. Later, we'd treat it with chlordane, and that worked great. The problem is DDT and chlordane stay in the muck forever, and now they're banned," Day said. "Besides, if you spray all the vegetation on the edge of the marsh with insecticide, you kill every insect that lands on that vegetation, not just sand flies.

"What we have essentially done is remove insecticide from the marsh. We bring the sand flies to the trap and catch them," Day said. "So we're not killing butterflies, fireflies, parasitic wasps or beetles or anything other than sand flies."

UF and Air Liquide, an international company that produces carbon dioxide gas, have patented the trap.

Source: Jonathan Day, 561-778-7200
-end-


University of Florida

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