Posting Date: February 1, 2010
Shock Waves from Wings Half a World Away
Have you heard about the "butterfly effect"?
Oddly enough, this has to do with weather prediction and a mind-bending field of science called "chaos theory." (Well, maybe it wouldn't bend your mind, but it certainly does mine.) Supposedly, back in 1961, an MIT scientist named Edward Lorenz wanted to find a way to combine mathematics and meteorology.
Lorenz was doing data runs on a mathematical model of the weather, using a dozen different equations. Two runs he did should have come out exactly the same, but didn't — and it turned out the problem was a single place in the data where a number should have stretched out to six digits, but had been rounded off to just three. That tiny "rounding-off" should have been totally inconsequential, but it actually made a huge difference in the outcome of the data!
Scientists call this "sensitive dependence on initial conditions." But it's also known by a much prettier name — "the butterfly effect" — which can be summed up as follows: A butterfly flapping its wings in Caracas, Venezuela, can affect the weather in, say, Chicago ... or New Orleans ... or Little Rock.
Mediterranean fruit fly, a worldwide agricultural pest. (Photo by Scott Bauer)
Here's why: If this moth ever makes it to the United States, it will wreak utter havoc in our citrus, corn, cotton and a wide range of nuts and fruits (and, as the song goes, those are a few of my favorite things!) So the ARS scientist is working to fight the moth in Africa, in hopes of stopping it before it begins to head our way, and secondly, ensuring a future weapon for us to use against it if it does show up on our shores.
What's particularly intriguing is the method he and his South African colleagues are using to combat this pest: the sterile insect technique, or SIT. This technique was pioneered by ARS scientists over half a century ago, and it's been a cornerstone of eradication programs used worldwide to control not only the screwworm, which was its original target, but also the Medfly, tsetse fly and other insect pests.
By one estimate, the ongoing SIT eradication program that's kept the screwworm fly out of the United States saves this country's livestock producers at least $900 million annually in potential losses. (If you'd like to read more details about how this amazing technique was developed, check out this link: http://www.ars.usda.gov/is/timeline/worm.htm)
The idea is that you irradiate male screwworm flies, just enough to sterilize them but not enough to seriously debilitate or kill them, and then you turn them loose to mate with wild female screwworm flies. The matings obviously don't result in viable eggs, and the screwworm population plummets at an astonishingly rapid rate.
The ARS scientist and his South African collaborators are using the same idea with a slight twist. Because a moth can't take nearly as much irradiation as a fly, they've backed off on the dosage, with the result that the female moths are totally sterilized and can't reproduce at all, and the males are either totally sterilized or partially sterilized. If the partially sterilized males mate with a wild female moth, eggs could result, but those eggs will be sterile, and thus ends the moth population!
The scientists have established a facility in a rural African village where they're raising, chilling, irradiating and transporting the codling moths to South African citrus orchards. In a single year of operations, sterilized moths released aerially or by hand have drastically reduced the populations of this month in South Africa's Western Cape region. The sterile moths also are available for shipment to the United States if they're needed here.
So, similar to the "butterfly effect," that's how a moth's love life in South Africa could have a big impact on our food supply here — and that's how an ARS scientist is helping make sure that doesn't happen!
The Agricultural Research Service is the chief in-house scientific
research agency of the U.S. Department of Agriculture. You can read
more about ARS discoveries at http://www.ars.usda.gov/news/.
About the author
"Everybody's
Science" is written by Sandy Miller Hays, Director of Information for
the Agricultural Research Service, the chief scientific research agency
of the U.S. Department of Agriculture. Hays is a native of Fort Smith,
Ark. From the late 1970s until early 1988, Hays was a reporter, editor
and columnist at the Arkansas Democrat (now the Arkansas Democrat-Gazette),
a Little Rock-based daily newspaper. She joined the ARS Information
Staff in 1988, and became Director of Information in April 1998.