Zappers Don’t Get Real Pests Devices Do More Harm Than Good, Scientists Say

Spring has arrived and daylight-saving time is here, so can the mosquitoes be far behind? For many Americans, it’s time to get out the electric bug zapper.

But wait, say some scientists who study insects. Too often, they believe, bug zappers not only are ineffective against biting bugs, but do more harm than good.

For instance, a study by the University of Delaware at Newark analyzed 13,789 insects zapped by electric traps and found only 31 - less than one-fourth of 1 percent - were biting bugs “seeking blood meals at the expense of homeowners.”

Nearly half were nonbiting aquatic insects that feed fish, frogs, birds and bats, the study found. And another 14 percent were insects that actually attack pests, such as wasps, ground beetles and ladybugs.

“The heavy toll on nontarget insects and the near absence of biting flies in catches suggest that electric insect traps are worthless for biting fly reduction,” concluded Douglas W. Tallamy and Timothy B. Frick, who conducted the study.

The Delaware study estimated that about 1 million zappers are sold in the United States each year. Through the 40 nights of the study, the seasonal mean catch per night was 445 insects per trap.

That means that if, in any given year, 4 million traps are used for 40 nights during the summer, then more than 71 billion nontarget insects are needlessly destroyed each year, the study concluded.

Some entomologists say the study suggested that since so many predators and parasites were killed, the traps may protect mosquitoes and other pests.

Electric traps typically use ultraviolet light to lure insects, which Tallamy said does not attract mosquitoes.

And, he said, mosquitoes are drawn away from the traps by the carbon dioxide exhaled by people.