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Title: Efficiency of Tank-Mixing Insecticide with Defoliant Against Adult Boll Weevil (Coleoptera:Curculionidae) Populations as Determined by Late-Season Field Disturbance Trapping

item Showler, Allan

Submitted to: Subtropical Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2008
Publication Date: 12/31/2008
Citation: Showler, A.T. 2008. Efficiency of tank-mixing insecticide with defoliant against adult boll weevil (Coleoptera: Curculionidae) populations as determined by late-season field disturbance trapping. Subtropical Plant Science. 60:58-65.

Interpretive Summary: There has been some controversy over whether or not insecticide tank-mix application with defoliant in preparation for cotton harvest can effectively suppress boll weevil populations. Large plots were used in commercial cotton fields to compare living adult boll weevil numbers collected in pheromone traps and numbers of dead weevils collected in screens on furrows where the defoliant was mixed with the insecticide cyfluthrin, where multiple large-capacity traps were deployed, and in control plots. The tank-mix was marginally more ineffective than multiple traps, and hence determined not to be particularly useful for suppressing boll weevil populations before the cotton-free winter season commences.

Technical Abstract: Large commercial field plots were used to assess the effect of tank-mixing cyfluthrin with a defoliant applied in preparation for cotton, Gossypium hirsutum L., harvest on adult boll weevil, Anthonomus grandis grandis Boheman, populations in south Texas during 2002 and 2003. The defoliant-insecticide tank mix reduced boll weevils compared to the defoliant-only control during the time between defoliant application and harvest in only one of the two experiments. During the same time interval, multiple trap deployment reduced weevil populations by at least as much as the tank mix. Tank mixing a single-pulse insecticide-defoliant treatment to prepare the crop for harvest, and deployment of multiple traps did not consistently affect boll weevil populations, but multiple traps reduced populations throughout the duration of each year’s experiment. Because of that, and logistical constraints associated with multiple trap deployment, adoption of mass trapping in cotton fields is not recommended, nor do we recommend tank-mixing an insecticide with a defoliant to achieve late-season control or suppression of boll weevil populations.