Flies, beware

Press, 28 December 1989, Page 11

Flies, beware

By

DONALD J. FREDERICK

National Geographic News Service

An ingenious fly trap developed by the U.S. Agricultural Research Service could be a boon to anyone plagued by the pesky disease-carrying creatures. In America, it has already been a hit with restaurants, nursing homes, ice cream parlours and landfills, as well as livestock farmers and their neighbours. The trap was devised as part of an aggressive fly control programme after Marylanders on a suburban subdivision near the Beltsville agricultural research centre gave the centre an ultimatum two years ago: Either control the flies or get rid of the farm animals.

The developer of the programme, Lawrence Pickens, hopes it will ultimately have a nationwide impact. “Until recently we’ve had trouble with baits,” Pickens says. “Some have contained dangerous ingredients; others have either been smelly, costly, or difficult to prepare. But now I think we’ve come up with a winner.” The experimental concoction contains sugar, baking powder, yeast, hdney, dried blood or fish

meal, and banana flavouring. Two small cubes of the bait, shaped in an ordinary ice tray, are placed in a pan of water beneath a. cylindrical aluminum trap. Once inside, the insects fly upward through a narrow cone, drawn by the sunlight that shines through the plexiglass top of the trap. They can’t escape, and starve to death within a day. As many as 20,000 flies can be captured in the trap before it has to be emptied. A little knowledge of fly behaviour makes traps and baits more effective. For instance, Pickens says, the insects cruise about a metre above the ground and like to fly along the edges of shrubs, fences, or rows of trees. Inside buildings they tend to go down near the floor and patrol the perimeter of a room. They have been known to cover eight km a day in seach of food.

Laboratory tests have convinced Pickens that flies can discern some differences in colours and have a natural affinity for light. The bright white “Beltsville pyramid,” another trap devised by the

entomologist, shows great promise and is being tested at farms in the region. An inexpensive plywood structure is covered with sheets of plastic treated with an adhesive that can snare 3,000 flies. The pyramid works better than other shapes because its surface reflects light uniformly, Pickens explains. Scientists at the centre are working on a weatherproof insecticide, harmless to animals, that would coat the pyramids. It would eliminate the nuisance of having to replace the sticky sheets when they became covered with flies. Richard L. Pugh, a Maryland dairy and grain farmer, credits the cylindrical traps with reducing fly-borne pinkeye disease among his heifers last year, and he has high hopes for the pyramids, which he has placed near his barns. “Flies have always been a major nuisance for the farmer,” he says. “In some cases they make life so miserable for cows that milk production is affected.”