Building A Better “Fly Swatter” Based on Science

Common house fly, Musca domestica."
Common house fly, Musca domestica.
This post is part of the Science Tuesday feature series on the USDA blog. Check back each week as we showcase stories and news from USDA’s rich science and research portfolio.
We’ve all heard the old saying, “You can catch more flies with honey than with vinegar.”  But that’s part of the problem where these germ-spreading pests are concerned:  House fly larvae can protect themselves against our most effective pesticides by burrowing deep into gooey substances like food, and adult house flies are very adept at developing resistance to pesticides. 
The scientists of the Agricultural Research Service (ARS) say they’re found an exciting alternative: a “fly swatter” in the form of a virus.  This new weapon, called salivary gland hypertrophy virus or SGHV, is a member of a newly discovered family of viruses called Hytrosaviridae.
Once a female house fly is infected with SGHV, her salivary glands swell up to huge proportions while  her ovaries remain small, and she can’t lay eggs.  That’s because the virus hijacks her body’s protein-manufacturing control system, and the protein that would normally go to make eggs is diverted to make SGHV particles. SGHV-infected male flies can’t mate.
As infected flies feed, they spew massive quantities of the virus particles on the food they leave behind.  When non-infected flies feast on the leftovers, they pick up the virus.
The scientists are testing ways to put this new “fly swatter” to work.  They’ve tried dipping flies in a solution of infected flies and water, or letting flies walk across a surface treated with the fly-water mix.  The results have been good, with an infection rate of more than 50 percent.
Although the scientists have focused principally on common house flies, other tests showed that the black dump fly and the stable fly are also significantly impacted by SGHV.  Stable flies are a significant economic pest that affects cattle, pigs horses and other large animals, and the flies can be a problem in recreational areas.
While the virus won’t ever be “quick fix” for flies at a picnic, for example, the scientists say it could become part of an integrated management program in which the virus is applied early in the year when flies start to reproduce—and it provides a promising template for the development of novel insect birth-control chemistries.


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