Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: December 15, 2008
Publication Date: N/A
Interpretive Summary: Boll weevil eradication commenced in the fall of 2005 for the second time after the first 2 short years of 1995 and 1996. Most of the cotton acreage under active boll weevil eradication is now within the state of Texas, and a significant portion of that is in the South Texas/Winter Garden, Upper Coastal Bend, and Lower Rio Grande Valley zones. Boll weevils were tested for susceptibility to malathion from 2004 to 2008 when enough cotton squares could be collected to conduct a valid assay from Hidalgo, Willacy and Cameron counties using a standardized topical assay. Over the years of study, no resistance to malathion was detected using this method. Plans are to continue conducting the assay as long as boll weevils can be collected from the Lower Rio Grande Valley.
Boll weevils were tested for susceptibility to malathion using a method that was standardized many years ago so that lethal dose values could be compared across years of monitoring. The lethal dose values as derived from probit analysis indicate that the boll weevil has been consistently susceptible to malathion when tested before the 2005 eradication effort, and up to 2008, where the lethal dose values did not increase after 3 years of multiple malathion applications. We believe the topical assays is the most accurate method for testing susceptibility of boll weevils to technical grade malathion diluted in acetone. Our intentions are to continue to monitor for resistance as long as weevils can be collected for conducting assays.