Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2016
Publication Date: 3/1/2016
Citation: Suh, C.P., Perez, J.L., Berg, A.L., Westbrook, J.K. 2016. Quantification of dichlorvos released from kill strips used in boll weevil eradication programs. Journal of Cotton Science. 20:26-30.
Interpretive Summary: Boll weevil eradication programs equip pheromone traps with insecticide-impregnated strips to kill and deter predation of captured weevils. The kill strips contain the insecticide dichlorvos and are typically replaced in traps on a 4-week interval. However, eradication programs have expressed concern over the duration of their effectiveness in traps. We quantified the weekly amounts of dichlorvos released from kill strips held in pheromone traps up to four weeks under a range of environmental conditions. Our results indicate that kill strips continue to release dichlorvos in traps up to four weeks. However, the amounts of dichlorvos released from kills strips during the third and, particularly, fourth weeks of aging in traps are likely too low to induce weevil mortality or to deter predation of captured weevils. Consequently, our results suggest reducing the replacement interval of kill strips in traps may ensure the benefits of their use are optimized or at least maintained.
Technical Abstract: Two types of kill strips, Hercon Vaportape II and Plato Insecticide Strip, are used by boll weevil, Anthonomus grandis (Boheman), eradication programs in the U.S. Both types utilize dichlorvos as the killing agent and are marketed to last up to a month in traps. Consequently, programs typically replace kill strips in traps on a four-week interval. However, published information on the duration of effectiveness of kill strips is not available and some programs have expressed concern over the duration of their effectiveness in traps. We quantified the weekly amounts of dichlorvos released from kill strips based on the weekly residual dichlorvos content of kill strips aged in pheromone traps up to four weeks. Three separate trials were conducted between May and November to cover a range of environmental conditions. On average, Hercon kill strips initially contained 61 mg of dichlorvos and released 33.0, 9.4, 5.0, and 2.0 mg of dichlorvos during the first, second, third, and fourth weeks of aging, respectively. Comparatively, Plato kill strips initially contained 93 mg of dichlorvos and released 35.6, 15.3, 9.9, and 7.3 mg of dichlorvos during the respective weeks. Although the quantity of dichlorvos needed to kill boll weevils in traps or to deter predation of captured weevils is not known, our results suggest the effectiveness of kill strips are substantially reduced with each week of aging in traps. As such, reducing the replacement interval of kill strips may be a consideration for optimizing or at least maintaining the benefits of their use in traps.