Catch more flies with blue than yellow

U. FLORIDA (US) — To limit the spread of disease, a new fly control device takes advantage of flies’ preference for the color blue.

Known as the Florida Fly-Baiter, the device is blue—in contrast to the yellow fly control devices on the market—and is far more effective, says Phil Koehler, a professor of urban entomology at the University of Florida.

As military personnel know firsthand, flies can spread diseases including dysentery, typhoid fever, and cholera, and they are often the first pest problem to occur when infrastructure, such as plumbing and electricity, is disrupted due to war or natural disaster, such as hurricanes and tsunamis.



Koehler and Roberto Pereira, an associate research scientist at UF’s Institute of Food and Agricultural Sciences, worked with two entomology graduates who are also in the Navy, Joseph Diclaro and Jeff Hertz, to develop the device.

As reported in the Journal of Medical Entomology, the key to making the device effective was the discovery that flies are three times more attracted to the color blue than to yellow and that yellow actually seemed to repel flies.

The device works by enticing flies using color, smell, and other attractants. Once at the device, the flies eat poisonous bait that quickly kills them. It does not trap the flies and so its usefulness isn’t reduced when it fills up with flies, like many other fly traps.

Pereira says that when testing the device, more than 40,000 flies were killed with one insecticide application. Additional insecticide can be applied as needed.

Researchers found the flies’ color preference by using behavioral tests that determined which color a fly was most likely to travel toward. Electroretinograms that measured the flies’ eye reaction found the insects responded more to blue as well.

Adding to the device’s effectiveness are black stripes covered with insecticide that line its outside. The stripes, tested and fine-tuned by Hertz, mimic dark crevices flies like to hide in.

Diclaro, who is lead author of the study and designed the device, says his time as a U.S. Navy hospital corpsman in Cuba in 1991, when Haitian refugees were flooding in, prompted him to work on fly control.

“At the time, there were so many displaced people living very closely together, and the garbage and waste accumulated, producing tons of flies,” Diclaro says. “I remember walking out of my tent and just being covered with them.”

Koehler says the fly control device can be used as an alternative to aerial pesticide treatments, which often attempt to cover too large an area to be effective.

“It’s a much more targeted way to deal with the problem,” Koehler says.

The device, which controls house flies, phorid flies and blow flies, is now available through pest control distributors. Insecticide is sold separately.

The Department of Defense’s Deployed War-Fighter Protection program, which seeks to better protect troops from insect-spread diseases, funded the research.

More news from the University of Florida: