Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2016
Publication Date: 12/1/2016
Publication URL: https://handle.nal.usda.gov/10113/5695432
Citation: Spurgeon, D.W. 2016. Captures of boll weevils (Coleoptera: Curculionidae) in relation to trap distance from cotton fields. Journal of Economic Entomology. 109(6):2405-2410.

Interpretive Summary: Once populations of the boll weevil are suppressed in cotton, eradication programs rely on traps baited with pheromone (a chemical mixture attractive to the weevil) for detecting weevils. If detection is not timely, the costs of remedial treatments are increased and population increases by the weevil may occur. Traps operated by eradication programs are traditionally placed in or near the outermost cotton rows where they may be subject to damage by farm equipment and loss of trapping data. Some programs have adopted a trap placement that is associated with, but outside the monitored fields. An ARS scientist at Maricopa, AZ showed that under high population levels of the boll weevil, traps placed 20-30 ft from cotton captured more weevils compared with traps placed adjacent to the outer row of cotton. When weevil populations were much lower, traps placed away from cotton and those placed adjacent to cotton captured similar numbers of weevils. In both years, the overall early-season patterns of weevil captures were similar for both trap placements. These results suggest numbers of captured weevils and the frequency of capture in traps placed away from cotton are at least as high as for traps adjacent to cotton. Therefore, relocation of traps away from the outer rows of cotton should not negatively impact ability to detect the boll weevil.

Technical Abstract: Once populations of the boll weevil (Anthonomus grandis grandis Boheman) are suppressed, eradication programs rely on pheromone trap-based monitoring for timely detection of weevil populations in cotton (Gossypium spp.). Delayed detection may increase the costs of remedial treatments, and permit reproduction by the weevil. Traps operated by eradication programs are traditionally placed in or near the outermost cotton rows where they may be subject to damage by farm equipment and loss of trapping data. Some programs have adopted a trap placement that is associated with, but outside the monitored fields. The influence of trap placement (near, =< 1 m from the outer row; far, separated from cotton by 7-10 m) on early-season weevil captures was evaluated. In 2005, during renewed efforts to eradicate the boll weevil from the Lower Rio Grande Valley of Texas, far traps consistently captured more weevils than traps near cotton. Traps at both placements indicated similar patterns of early-season weevil captures, which were consistent with those previously reported. In 2006, no distinction between trap placements was detected. As in 2005, early-season patterns of captures in 2006 were similar for both trap placements, but captures were much lower and irregular compared with those observed in 2005. These results suggest magnitude and likelihood of weevil capture in traps placed away from cotton are at least as high as for traps adjacent to cotton. Therefore, relocation of traps away from the outer rows of cotton should not negatively impact ability to detect the boll weevil.