INFLUENCE OF FRUIT ON SAMPLING AND CONTROL OF ADULT BOLL-WEEVILS IN COTTON

The influence of cotton fruit on boil 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 n ot effectively collected by pneumatic or drop cloth techniques. The pn eumatic sampler collected approximate to 70% of weevils not associated with fruit. Overall collection efficiency (marked weevils) averaged 1 3% in the presence of fruit and 21% when fruit were removed. Mortality of adult boil weevils resulting from treatment of cotton plots with f ipronil and azinphosmethyl were evaluated using beat net, whole plant, and fruit census techniques. Neither material significantly reduced t he number of adult weevils residing in protected sites when applied on a 7-d interval; howevever, a significant reduction occurred when trea tments were applied at 3-d intervals. Fipronil was more efficacious th an azinphosmethyl, based on the percentage of squares punctured. Howev er. a higher density of both infested and uninfested squares occurred in the fipronil plots and reduced boil weevil population recruitment w as not demonstrated. Similarity of adult bull weevil population trends among treatments indicated plot size was too small to prevent interpl ot movement. Our results illustrate the importance of considering weev ils located in fruit refugia during sampling evaluations, and the impl ications of these populations in efficacy trials.