Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 4, 2006
Publication Date: August 1, 2006
Citation: Showler, A.T. 2006. Boll weevil (Coleoptera: Curculionidae) damage to cotton bolls under standard and proactive spraying. Journal of Economic Entomology. 99(4):1251-1257. Interpretive Summary: In some parts of the boll weevil's distribution, insecticides are applied after cut-out when bolls are the predominant stage of fruiting body. This study demonstrates that the standard spray regime in south Texas, which involves insecticide applications after cut-out, did not result in more bolls than in a nontreated control. An alternative "proactive" spray regime that focuses on protecting large squares before cut-out resulted in 1.9- to 2-fold more bolls in the lower half of the canopy than the control. The percentage of damaged boll carpals was 2-fold greater in the standard treatment lower canopy than in the proactive treatment, and the percentage in the control was 1.8-fold greater than in the standard treatment at one of two experimental field locations. Percentage of damaged carpals in the proactive treatment upper canopy was 1.5-fold greater than in the control at the other field location. In the control and standard treatments, percentages of upper canopy clean bolls were lower than or not different from percentages of bolls with 1, 2, 3, or all carpals damaged, but in the proactive treatment, percentage clean bolls in the upper canopy were mostly greater than percentages of bolls with 1, 2, 3, or all carpals damaged. Reasons for the lack of effectiveness of the standard treatment and the benefits observed in the proactive treatment are discussed.
Technical Abstract: The extents to which boll weevils can damage bolls and the influence of insecticide sprays and their timing in relation to cotton fruit development were both not well understood. This study demonstrates that proactive spraying, which targets large squares only, is more effective than the standard approach, which entails spraying when bolls become predominant, in terms of numbers of boll carpals that were damaged by developing boll weevils. Lint yield is significantly increased as a result of timing sprays to coincide with large square production, and economic return is also increased because fewer sprays are required in the proactive approach.