Although zapping insects with ultraviolet bug killers is gaining popularity these days, the electronic devices are running into a hornets' nest of controversy. Some experts say they're not as effective as advertised.
After three summers of research, Dr. T. Michael Peters, a professor of entomology at the University of Massachusetts in Amherst, finds that the light traps are ''not terribly'' effective for controlling backyard populations of pest insects. A prime reason, he says, is that many species of mosquitoes and other bugs are not attracted to the lights.
In fact, the greatest effect of light traps is psychological, Dr. Peters says , because homeowners can hear insects being electrocuted.
Even manufacturers agree that the bug killers don't eliminate all pesky insects.
Light traps are ''an aid, not a cure-all,'' says Duane Osterkamp, executive vice-president of Flowtron Division of Armatron International Inc. of Melrose, Mass., which claims to manufacture 60 percent of the ultraviolet bug killers sold in the United States.
''You always have insects in the area,'' because some ''do get blown in,'' Mr. Osterkamp says. But with electronic bug killers, ''you can put a real dent in the numbers of insects reproducing in the immediate area.
''That's not to say you're not going to be bitten by a mosquito, but you're not going to be bitten by as many of them.'' Osterkamp cites as evidence US Department of Agriculture (USDA) data from the early 1900s that determined that ultraviolet, or black, light is the best source for attracting a wide range of insects, including some mosquitoes, moths, flies, and other insects that fly at night.
The June issue of Consumer Reports, which appears May 27, carries a report on the ultraviolet bug killers. The publication's home-testers found that the more effective models of ultraviolet bug killers did have some effect on mosquito populations in backyards, according to Sylvia Hemp, a spokeswoman for Consumer Reports.
But, the report adds, ''in contradiction to some earlier studies by USDA, recent studies by some universities have cast doubts on black light as an effective control for mosquito infestation.''
A yard's insect population of any species cannot be reduced substantially, according to Dr. Peters, because many insects of the same species live in the surrounding area. ''The effect of a few light traps will not be noticed,'' he says.
Peters says that some electronic bug killer manufacturers claim that the instruments can attract mosquitoes from further distances than are actually possible.Mosquitoes can be attracted from ''no more than a short distance,'' he says.
Armatron's bug lights, for example, which range in cost from $50 to $230, attract insects from 80 to 125 feet away, according to Mr. Osterkamp. Electronic grids surrounding the lights electrocute the insects.
But, adds Peters, even some insects that are attracted to light traps lose their interest in the ultraviolet light upon approach.It is possible that homeowners ''could attract pest insects (and) might end up with a worse problem'' in this way, he says.
Clifford Chater, an entomologist with the University of Massachusetts at the Suburban Experiment Station in Waltham, says that many garden pest insects are attracted to electronic bug killers when they are at a stage in their life cycles when they cannot harm plants. For example, cutworm moths are attracted and killed by light traps. But these adult forms of the cutworm do not eat vegetable crops, having already chewed through the stems of tomato plants and other crops in an earlier stage as immature larvae, according to Mankowsky.
According to Peters, the cutworm moth is attracted to electronic bug killers only after it has laid eggs. The eggs can develop into a future cutworm population.
Peters and Mr. Chater say that ultraviolet bug killers cannot control gypsy moth populations, as many people think, because female gypsy moths are not attracted to light traps. Even if four-fifths of the male gypsy moths -- which are a tremendous problem for the Northeast - were killed by ultraviolet bug killers, the remaining males could fertilize all the local female gypsy moths, he says.