[Annual Fly Control Issue] From science to service

One of the rites of passage of being a parent is helping your child with his or her high school science fair project. Countless volcanoes have been built, mice run through mazes and potatoes hooked up to conduct electricity. But if the parent is an entomologist, chances are the project will focus on insects.

That was exactly the scenario Dr. Russell Mizell III found himself in about 12 years ago. Driving along the edge of a field in the country, he noticed that deer flies were chasing the mirrors of his truck. This phenomenon, he reasoned, would make a great science project for his son.

HABITAT AND BEHAVIOR. Deer flies are active for the most part during daylight hours but a few feed after dark. Some are more active in the morning or evening. Adult deer flies spend a large portion of their time resting on vegetation. Adult deer flies are present from early spring to late fall but each species has its own period. Adult deer flies are swift, strong fliers and may fly more than a mile from their breeding areas. Most deer flies require a blood meal to develop eggs. However, they also feed on pollen, nectar and perhaps insect excreta, honeydew.

Eggs of most deer flies are placed on vegetation in moist areas. Most immatures or larvae are found in water or wetlands and are predacious on other organisms or eat vegetable matter. Tabanids as a group can mechanically transmit (on their mouthparts) disease organisms such as bacteria, viruses, trypanosomes and rickettsia. They also have their own natural enemies such as dragonflies, wasp, spiders and birds.

Deer fly larvae are found at the edges of bodies of water. “They come out of their pupation area and move to a habitat they like and sit there and wait for prey to go by,” said Mizell, a professor of entomology at the University of Florida Institute of Food and Agricultural Sciences in Quincy, Fla. Normal habitats include edges of forests and fields, with bicycle, walking and bridle path areas particularly prone to infestations.

Female deer flies need blood meals to lay eggs, and will land on livestock, wildlife, pets and humans. Their bites can be painful and even lead to allergic reactions in some people. “How deer flies search for food and move through the landscape is important for PCOs to understand,” he said. Even though there are different species of deer flies, for the most part, their behavior is similar.

In addition, in cooler temperatures they are not as active, and do not fly at night or in windy conditions.

SCIENTIFIC METHOD. Mizell had studied the structure of commercial deer fly traps and most looked like inverted funnels with a moving part at the bottom to attract the flies. Since his son was going to use common household objects for his science project, they decided to try various sizes of plastic flowerpots.

Tests were conducted with various sizes of pots, and they found the optimal size was 6 inches in diameter. With that variable determined, he focused on color, using black, red and blue pots. The flies showed a propensity to the color blue, so Mizell experimented with different shades and found the brighter the hue, the more the deer flies were attracted.

When testing was completed, Mizell concluded the following: the height of the trap should be between 3 and 6 feet high, since a deer fly attacks the highest spot on its prey; movement is necessary — the trap could not remain stationary because deer flies tend to attack an object in motion; the optimal speed during trolling is less than 7 miles per hour; bright blue is favored; the size of the trap should be around 6 inches in diameter; contrast between the trap and its surroundings should be distinct; and an adhesive must coat the outside surface to catch the flies and be reapplied liberally.

When used properly, the Trolling Deer Fly Traps are highly attractive to deer flies or pine flies in the genus Chrysops, which are most of the species that are bothersome to people. Most deer flies attack people and pets around the head, neck and shoulders. (Yellow flies usually attack the legs.) The trap is effective because the flies respond to the trap’s motion, color and size. The trap is covered with a special sticky material that catches the flies when they land.

MAKING DEER FLIES PAY. Mizell stressed it is important for PCOs to learn, based on their geographic location, when deer flies are most prevalent. “Your local county agent knows how many phone calls the office receives about various pests, and you can pinpoint when deer flies are a problem,” he said.

Mizell’s trap is effective because the flies respond to the trap’s motion, color and size. Localized trolling is in typical deer fly habitats can yield great results. (“Trolling” means mounting the trap on a vehicle, tractor or front or back [front is best] of a lawnmower or four-wheeler, and driving around an area several times slowly [less than 7 mph.]) Doing so will reduce the deer fly populations considerably until new flies arrive because the 6-inch blue pot will catch large numbers of deer flies. “With the right presentation, you can go around once or twice and you have them all,” Mizell said. But he warns PCOs not to make the claim to clients that deer flies will be eliminated. “It’s only for a period of days. You’re not reducing future populations” that are still in the larval stage.

For instance, a PCO can troll with the deer fly trap around the perimeter of a client’s backyard before a summer outdoor party. “You can eliminate the deer flies (for that event) since there are a finite amount,” Mizell said. “The customer will be happy.”

Other venues with the potential to benefit from this deer fly trap trolling would be racetracks, golf courses, zoos, amusement parks, biking and hiking trails, and anywhere people congregate in favored deer fly habitats.

If a client presents a situation with both deer flies and horse flies, it will “require you to integrate your tactics, and it becomes trickier,” he said. In this case, trickier could translate into additional revenue.

The author is a frequent contributor to PCT magazine.

For more information…
To learn more about the Trolling Deer Fly Trap, and for detailed directions on how to make one, visit http://ufinsect.ifas.ufl.edu/deerfly_trap.htm.