Interference of boll weevil trapping by spiders (Araneida) and an evaluation of trap modification to reduce unwanted arthropods

Authors: Armstrong, John; RICHMAN, D - NEW MEXICO STATE UNIV

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2007
Publication Date: 8/27/2007
Citation: Armstrong, J.S., Richman, D. 2007. Interference of boll weevil trapping by spiders (Araneida) and an evaluation of trap modification to reduce unwanted arthropods. J. Entomol. Sci. 42(3):392-398.

Interpretive Summary: The eradication of the boll weevil (Anthonomus grandis grandis Boheman) from the United States is becoming closer to reality as active programs are now in place in South Texas. The boll weevil trap is the ultimate tool for monitoring populations, and the key tool used in making treatment decisions on large acreages of cotton. We evaluated a boll weevil trap modified for reducing unwanted arthropods that enter the trap and prey on boll weevils, or obstruct the entrance hole of the trap by webbing. Either method of trap interference is a reduction in trap efficiency. Our modification did not prevent spiders and some other insects from entering the trap, however we discovered a spider from the family Araniedae, a spider with an instinctive web spinning behavior, was the most prevalent spider found in the boll weevil traps. We also discovered that when a boll weevil trap is obstructed with webbing during the course of one week operation, it results in a 58% reduction in the mean number of boll weevils captured. This study is the only one of its kind that addresses arthropod interference in boll weevil trapping and suggests that a kill-strip that is active against both insects and spiders should be used to monitor boll weevil populations in South Texas. It is imperative that the most efficient boll weevil trap available be used for the completion and successful maintenance of eradication.

Technical Abstract: Our evaluation of a boll weevil trap modified to reduce the number of unwanted arthropods had little effect on reducing spiders, the arthropod species that made up > 95% of the individuals that entered boll weevil (Anthonomus grandis grandis Boheman) traps and interfere with weekly capture of boll weevils. When spiders obstructed the entrance of a boll weevil trap with webbing, there was a 58 % reduction in the mean number of weevils collected on a weekly basis. We believe that spiders from the family Araneidae are key to the interference of boll weevil trapping because of their instinctive habit of webbing over the entrance of the boll weevil trap. Other spider families may be responsible for obstructing the entrance of the cone, however their webbing habits are unknown to us, and they are generally in lower densities that Araneids. The results of this study conclude that spiders can significantly affect boll weevil trapping efficiency in South Texas. This is an important finding, because South Texas is the last area of active eradication, and detecting low number of weevils and operating boll weevil traps that are as efficient as possible will be critical to keeping the boll weevil out of the United States.