Originally created 08/05/98

Group developing trap for fighting sand gnats



SAVANNAH -- A Florida entomologist and a Texas-based company are developing a means of fighting back against that scourge of the Eastern seaboard -- the sand gnat.

The tiny critters thrive from Maine to Texas under a variety of names: sand gnats, sand flies, no-see-ems, moose flies or "flying teeth."

Unlike mosquitoes, which thrive in standing water and can be fought using a variety of methods, it's harder to hit sand gnats in the marshes where they hatch without damaging other creatures in the ecosystem.

Dr. Jonathan Day, a professor of research entomology at the University of Florida, is using a different approach. Dr. Day developed a means of attracting and killing sand gnats when they invade our parks, playgrounds and lawns.

His invention resembles a five-gallon paint can on a post, with the sides of the can covered with a fine black mesh fabric.

A combination of carbon dioxide and octenol, which the sand gnats are drawn to by their sense of smell, is piped through the top of the can through a line from a tank. The mesh is coated with either mineral oil or insecticide.

The gases trick the gnats into thinking they're on their way to feasting on a human or other red-blooded animal. When the gnats get to within five to 10 feet of the trap, they're drawn visually to the black mesh.

Octenol is a form of alcohol -- which can be produced synthetically -- contained in the breath of a water buffalo.

"They fly in and hit the mineral oil and once they hit the mineral oil that's it," Dr. Day said.

He said the traps can attract gnats from 80 yards to 500 yards depending on wind conditions.

Rather than simply being a means of control, Dr. Day said his traps are intended to be used more as a means of defense. A line of traps could be constructed between a marsh and a playground, for example, to reduce the number of gnats flying in for a feast.

"It would be wrong for me to tell you that we can eliminate sand flies," said Joe Paganessi, a senior engineer at Air Liquide America Corp., the Houston-based company that is developing the traps for commercial use. "We reduce the population but we're not eliminating them from breeding."

Air Liquide has a Savannah operation that supplies Kemira.

Dr. Day said sand gnats -- because of their size -- play no significant role in the food chain.

Under a four-year test in Vero Beach, Fla., Dr. Day set up 18 traps and collected 160,000 sand gnats per trap each day his first year. In the second year the kills fell to 16,000 per day, and in the third year to just 1,600 per trap each day.

When insecticide is used instead of mineral oil, the traps can be used against other flying vermin such as mosquitoes and deer flies.

The company intends to market the product for commercial applications. Mr. Paganessi said sites in the 20-acre to 30-acre range are suitable, although areas as small as five acres might be used.

Dr. Day estimates his operating costs at $40,000 a year, although Mr. Paganessi said it's hard to say what the company will charge. Air Liquide hopes to begin marketing the traps by the end of the year.

The concept of these traps makes sense to Henry Lewandowski, director of Chatham County Mosquito Control, but he hesitates to say whether it is practical until hearing more about their effectiveness.

The county employs various means of fighting mosquitoes, but attacking sand gnats offers environmental and logistical problems, Mr. Lewandowski said. The county fights mosquitoes where they hatch in standing water by draining rainwater into canals where fish feed on the mosquito larvae.

Mosquito Control also hits mosquitoes at their source by spreading mineral oil on ponds, keeping juvenile mosquitoes from breathing on the surface of the water. The control also sprays the synthetic hormone methoprene, which keeps the mosquitoes from maturing properly.

Mr. Lewandowski said the county traps and monitors mosquito populations and can also spray malathion from the air in problem areas.

Sand gnats, on the other hand, grow in marshes, where attacking them would cause environmental damage to sand crabs and other creatures.

"Everybody keeps talking about it, but it's just not cost-effective," Mr. Lewandowski said.