Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 1997
Publication Date: N/A
Interpretive Summary: The logistics of effectively sampling adult boll weevil populations over large areas make it difficult to evaluate their entry patterns in cotton fields. A tractor mounted forced air sampling device was designed and constructed that facilitates such large area sampling. We compared the efficiency of this sampling device for sampling adult boll weevils in cotton with fruiting forms present and in cotton where the fruit had been removed from the plants. We also investigated the effects of adult boll weevils residing under the fruit bracts on evaluating the effectiveness of pesticides. Our studies showed that a large proportion of the adult weevils were normally hidden under the fruit bracts and that these weevils could not be sampled without removing the fruit. However, the forced air sampling device was effective in sampling weevils not hidden under the fruit bracts. Our studies also showed that weevils hidden under the fruit bracts were not impacted by the application of pesticides. The results show the importance of considering weevils hidden under fruit bracts in sampling evaluations and the importance of these weevils on evaluating the effectiveness of insecticides.
Technical Abstract: 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 sampled by pneumatic or drop cloth sampling. The pneumatic sampler collected 68.4% (unmarked) to 75.9% (marked) of weevils not associated with fruit. Overall collection efficiency (marked weevils) averaged 13% in the presence of fruit and 21% when fruit were removed. Efficacies of fipronil and azinphosmethyl against boll weevil were evaluated. Beat net and whole plant samples indicated boll weevils located in protected sites were poorly impacted by pesticides. Efficacy of fipronil was indicated by reduced percent of squares punctured, however fruit counts indicated a higher density of both infested and uninfested squares in fipronil plots. Although more undamaged fruit were present in the fipronil treatment than in other treatments, boll weevil population recruitment was not reduced. Similarity of adult boll weevil population trends among treatments indicated plot size was too small to prevent inter- plot movement. Our results illustrated the importance of considering weevils in fruit refugia, in sampling evaluations, and the implications of these populations in efficacy trials.