"We wanted to develop a method where the producer could apply a single treatment and be done," Taylor says. "They can quickly treat sites while doing other chores or checking on cattle."
Luring Flies to Drive Them Away
Another technique for controlling stable flies involves identifying natural compounds that drive them away and developing attractants to lure them into traps.
AMRU entomologist Jerry Zhu calls this his "push and pull" strategy. The "push" forces stable and other filth flies away from host animals, and the "pull" entices flies into traps—baited with low-toxic insecticides, sticky substances or a combination—to kill them.
Zhu is experimenting with plant-based chemicals like catnip to drive filth flies away from livestock.
"Catnip oil and its active compounds—nepetalactones—are powerful repellents against stable flies," Zhu says. "To date, it's probably the best repellent identified for flies that bite. It's also good at reducing larval development."
Several sprayable catnip oil formulations that decrease stable fly field populations have been developed by Zhu and his colleagues. They have also worked with Microtek Laboratories, Inc. of Dayton, Ohio, to test a new granular catnip product that prevents flies from laying eggs.
Killing Flies with a Virus
At the ARS Center for Medical, Agricultural and Veterinary Entomology (CMAVE) in Gainesville, Fla., scientists have found that a potential biological control agent—salivary gland hypertrophy virus (SGHV)—that's been experimentally successful in controlling house flies also kills stable flies.
Collaborating with scientists at the University of Florida and Denmark's Aarhus University, entomologist Chris Geden in the Mosquito and Fly Research Unit at CMAVE studied the distribution and host range of the virus, and the effectiveness of different SGHV application methods.
SGHV is one of three viruses known to occur in pests they infect, Geden says. The virus replicates in the salivary gland and multiplies in female flies. The salivary glands increase in size, while ovaries remain small. Female flies infected with the virus never produce eggs again, and male flies do not mate.
Healthy house flies are believed to contract the virus after feeding on contaminated food particles left by infected flies. The virus, which was successful at stunting the growth of house flies, also severely affected stable flies in an experiment.
"When we injected stable flies, not only did they become infected, but they died very quickly. Of those that didn't die, many did not have developed ovaries," Geden says. "Also, infected stable flies produced 50 percent to 75 percent less feces, suggesting that they weren't feeding on blood or biting as often as healthy flies."
Stable flies that had the virus did not lay eggs, did not bite as much and had a significantly shorter lifespan than uninfected pests, Geden says.