Influence of fruit on sampling and control of adult boll weevils in cotton

The influence of cotton fruit on boll weevil collection efficiency by a tractor-mounted pneumatic sampler was evaluated. In fruiting cotton, most adult weevils were found within the bracts of squares and were not effectively collected by pneumatic or drop cloth techniques. The pneumatic sampler collected approximately 70% of weevils not associated with fruit. Overall collection efficiency (marked weevils) averaged 13% in the presence of fruit and 21% when fruit were removed. Mortality of adult boll weevils resulting from treatment of cotton plots with fipronil and azinphosmethyl were evaluated using beat net, whole plant, and fruit census techniques. Fipronil was more efficacious than azinphosmethyl, based on the percentage of squares punctured. However, a higher density of both infested and uninfested squares occurred in the fipronil plots and reduced boll weevil population recruitment was not demonstrated. Similarity of adult boll weevil population trends among treatments indicated plot size was too small to prevent interplot movement. Our results illustrate the importance of considering weevils located in fruit refugia during sampling evaluations, and the implications of these populations in efficacy trials.