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In late summer of 2007, cotton growers in Texas's Southern Rolling Plains had reason to be alarmed. Hundreds of boll weevils were turning up in their fields. By the end of the year, more than 6,000 weevils were found in monitoring traps spread across several counties where the insect had been eradicated since 2000.
But a team of Agricultural Research Service scientists with a variety of skills was able to track down the likely origins of the reinfestation, giving cotton growers and entomologists some guidance on how to eradicate them and shedding light on just how far boll weevils can travel under certain conditions.
Boll weevils have been a threat to cotton growers since 1892, when they entered Texas from Mexico and proceeded to invade much of the south-central and southeastern United States. Large-scale eradication efforts, begun about 30 years ago, eliminated the boll weevil from much of the southern United States, but they remain a problem in pockets of eastern and southern Texas. Successful eradication efforts drastically reduce pest-management costs and insecticide use. Reinvasion is a constant threat, even in areas where they have been eliminated. Guarding against reinfestation is coordinated by the growersupported Texas Boll Weevil Eradication Foundation, which funds monitoring programs and insecticide applications throughout the state.
"Whenever eradication personnel capture boll weevils where they're not expected, they want to know everything possible about where the weevils may have come from. That information plays a major role in deciding the most appropriate response," says Thomas Sappington, an ARS entomologist in the Corn Insects and Crop Genetics Unit in Ames, Iowa. If the infestation is small scale, eradication personnel may need to spray only a few surrounding cotton fields. But if there is evidence of a widespread reinvasion, they...