Genetic GPS for Tracking Boll Weevils
By Ann Perry
August 23, 2007
Fortunately, the boll weevil
(Anthonomus grandis), which devastated U.S. cotton crops for much of the
20th century, is now found only in parts of the mid-South and South Texas,
thanks to eradication efforts. But monitoring weevils to keep track of where
they are coming fromand where theyre goingis vital for
protecting cotton crops in the United States.
Agricultural Research Service (ARS)
Sappington works in the ARS
Insects and Crop Genetics Research Unit at Ames, Iowa. He has tracked local
weevil movements by marking the insects with enamel paint or fluorescent
powders and recapturing them later. Now he uses
microsatellitesshort, repetitive DNA sequencesand
population assignment tests to find out where weevils in different populations
have come from. These tests help pinpoint the migratory patterns and origins of
boll weevils over long distances.
Of course, the weevils dont respect international borders. In 2004, a
small group of boll weevils was found next to an eradication zone in Durango,
Mexico, where weevils had not been reported for about 10 years. Sappington
compared weevil microsatellites from this group to four other weevil
populations from northern Mexico and southern Texas.
His analysis determined that some of the weevils in this group were
immigrants. But most of them belonged to a previously undetected resident
population that had suddenly increased because of greater rainfall levels. His
findings also indicated that final weevil eradication efforts in Texas were
being hindered by weevil migration within Texas and from Mexico.
Sappingtons work demonstrates that powerful microsatellite markers and
population assignment tests are practical tools for identifying the origins of
boll weevils found in areas that have previously been weevil-free. In addition,
identifying boll weevil migrants within established weevil populations and
knowing where these new migrants came from will foster better strategies for
monitoring and managing boll weevil pest introductions throughout North
more about this research in the August issue of Agricultural
ARS is the U.S. Department of
Agriculture's chief scientific research agency.