Deer Flies A Biting Problem? Oddly, "Trolling" May Be Just The Ticket

August 13, 2002

GAINESVILLE, Fla. — The deer flies are so bad at Dick Coski’s farm near Lake Erie in northeast Ohio that he used to get covered in bites mowing his small field.

Hunting for a solution, the retired Social Security claims representative found a Web site about a curious deer fly-control device invented by a University of Florida scientist. The bright blue plastic flowerpot, covered with sticky material and suspended upside-down on a pole, was said to entice and capture the pesky bugs.

It looked goofy. But when Coski, 70, rigged up a similar device and stuck it on the front of his John Deere, he was amazed at the result.

“The deer flies didn’t even look at me – they were all buzzing around that darn flower pot,” Coski said. “My sister-in-law’s husband is one of those hard-nosed Englishmen, and he didn’t believe me. He came up from Columbus and took a ride on my lawn tractor, and he couldn’t get over it.”

Insects are strange creatures that sometimes prove vulnerable to even stranger methods of elimination. That seems to be the lesson of the curiously effective deer-fly trap invented by Russell Mizell, a professor of entomology at UF’s Institute of Food and Agricultural Sciences. Mizell’s article about the trap appeared in the June issue of the journal Florida Entomologist, although it previously was featured on an IFAS pest-control Web site.

Mizell, who is based at UF’s North Florida Research and Education Center in Quincy, said he first launched the research several years ago as a high school science project with his son, but “it got so interesting, I just kept doing it.”

He was familiar with reports that African tsetse flies are drawn to silhouettes of hoofed animals. He also had noticed that deer flies often buzzed the rearview mirrors on his truck as he drove along the gravel driveway to his Jefferson County home. Deer flies are so-called ambush predators: They wait for prey to walk by rather than actively searching for it, so they are highly attracted to movement.

With this in mind, Mizell and his son decided the best way to snare deer flies likely was to “troll” for them from a slow-moving vehicle. Working in the spring and summer when deer flies are most prominent, they “did all kinds of crazy things” to try to discover what kind of trap worked best, he said.

The Mizells first tried draping their 1992 Dodge Dakota pickup with white plastic covered with black silhouettes of various shapes painted with Tanglefoot, a commercially available sticky spray for insects. But the deer flies snubbed the silhouettes. Theorizing that three-dimensional shapes would work better because they had more surface area, the Mizells built a test platform on their truck hood that could troll seven different shapes at once. They ambled along in deer fly-infested countryside for set periods of one to five minutes, testing sticky pyramids, squares, balloons, plant containers and other shapes, then counting immobilized prey. They also tried black, tan, blue and shapes of other colors suspended from various heights.

After numerous experiments, the trap that wooed the most deer flies proved to be a 6-inch flower pot painted bright blue – capturing as many as 30 deer flies in a one-minute test. It worked best when suspended three to six feet above the ground and trolled no faster than 10 feet per second.The capture rate was 35 percent to 50 percent higher than for other shapes, Mizell said.

Mizell said he isn’t sure what it is about this color/shape/speed combination that makes it so irresistible to the hapless deer flies. It could be that something about it appeals to their genetic memory of a tasty but extinct animal. But more likely, he said, the blue contrasts sharply with the predominant background of green foliage, making it easy for the deer flies to zero in on. The optimum size and height, meanwhile, are close to the head of a person or large animal.

The traps are remarkably effective, Mizell said. “Many times after running the traps through an area, we found there were no deer flies left,” he said. “You trap them out for a short period until they repopulate the area.”

The traps do not have to be suspended from a vehicle – they also work when attached to a baseball cap and trolled by the hat’s wearer.

After hearing Mizell give a presentation on his project, Wendy Meyer, a staffer at the UF Tropical Research and Education Center in Homestead, decided to try out such a rig to combat the deer flies that attacked her during her field research. Wanting to avoid wearing a flowerpot, she used a blue soda cup painted with Tanglefoot.

“It worked wonderfully,” she recalled. “I’d come back in, and I’d have 10 or 12 flies on my cap and none that had annoyed me.”

Despite its effectiveness, it is doubtful the trap ever will gain widespread appeal for personal protection. As Meyer noted, its aesthetic appeal leaves something to be desired.

“The thing is, it looked really silly, so everyone laughed at me when I wore it, but then they complained about getting bitten by deer flies,” she said. “It’s a hard sell to get people to try it, but it really did work.”