Restaurants and supermarkets could save millions of dollars by hanging on to bug zapper bulbs instead of tossing them every year as they normally do, a new University of Florida study has found.

What’s more, the benefits could extend to the environment by keeping some of the bulbs’ mercury out of the waste stream.

Phil Koehler, an entomology professor in UF’s Institute of Food and Agricultural Sciences, presented study findings last week at a conference of the National Pest Management Association in Phoenix.

John Cooksey, a doctoral student working with Koehler, helped present the study. In addition to his doctoral work, Cooksey owns a pest management company in Jacksonville and is president of the Florida Pest Management Association.

Koehler said he and Cooksey examined 20 insect light traps over the past year because they’re the prime method to control flies in restaurants, supermarkets, and other commercial establishments. They wanted to know if users of commercial-grade traps could use bulbs for longer periods of time while maintaining effective pest control.

“Whenever you go into a restaurant, there’s usually a light trap there that’s designed to catch the flies,” Koehler said. “It may look like a sconce on the wall, but it probably is a light trap.”

In their study, Koehler and Cooksey found that 13-month-old bulbs caught about 80 to 90 percent as many flies as the new bulbs caught. That’s good news on two fronts, Koehler said.

One is financial.

Cooksey has some large commercial contracts, Koehler said. He and Cooksey discovered that changing bulbs on just one large commercial contract could cost around $15,000. Each bulb costs only about $10, but a large commercial contract might require as many as 1,500 bulbs, Koehler said.

The second good news to come from the study is on the environmental front.

“Most fluorescent bulbs used in insect light traps contain mercury,” Koehler said. “They’re recyclable, and you try not to throw them out in the trash, but you know some will end up there. The more often you throw away these bulbs, the more potential for environmental contamination.”

The $10,000 grant that supported the study came from the National Pest Management Association Foundation.

The only data available from the pest management industry comes from bulb manufacturers, who maintain that bulbs don’t emit as much light after a year, and that is true, Koehler said.

“But no one ever asked: are those old bulbs as attractive to flies as the new ones?” he said. “When is it time to throw the bulb away, based on the fly, rather than the manufacturer?”

The study is continuing to review bulbs’ attractiveness to flies as the bulbs age.