Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2016
Publication Date: 10/1/2016
Citation: Suh, C.P., Spurgeon, D.W. 2016. Boll weevils (Coleoptera: Curculionidae) continue to release pheromone following host removal. Journal of Entomological Science. 51(4):332-335.

Interpretive Summary: Our prior observations suggested a substantial proportion of boll weevils captured in pheromone traps may continue to release pheromone. Such an occurrence could confound interpretation of trapping results, particularly those involving evaluations of new lure formulations or trap designs. We examined the duration and quantities of pheromone released by boll weevils following their isolation from food, as would be the case for weevils captured in traps. Our results conclusively demonstrate that pheromone-producing boll weevils can continue to release relatively small quantities of pheromone for at least four days following their removal from a food source. However, the full extent of this potentially confounding factor in trapping studies will likely depend on the numbers of pheromone-producing weevils captured and the elapsed time when weevils last fed prior to their capture in traps. Nonetheless, our findings illustrate a previously unrecognized or disregarded occurrence which should be considered in boll weevil trapping studies.

Technical Abstract: Pheromone traps are a key component of management and eradication programs directed against the boll weevil, Anthonomus grandis (Boheman), but trap data remain difficult to interpret because of the day-to-day variability in captures. Our prior observations suggested a substantial proportion of boll weevils captured in traps may continue to release pheromone. Such an occurrence could confound interpretation of trapping results, particularly those involving evaluations of new lure formulations or trap designs. We conducted a study to confirm whether boll weevils continued to release pheromone following their isolation from food, as would be the case for weevils captured in traps. All tested weevils continued to release small quantities of pheromone during the first day of food removal, but only 64, 27, and 9 percent of these weevils continued to release pheromone on the second, third, and fourth days of starvation, respectively. Correspondingly, pheromone production was reduced by approximately 75 and 97 percent on first and second days following food removal, respectively. By the third and fourth days of starvation, pheromone quantities averaged less than 1 percent of the initial pheromone levels of weevils measured just prior to food removal. These results conclusively demonstrate that pheromone-producing boll weevils can continue to release small quantities of pheromone for at least four days following their removal from a food source. However, the full extent of this potentially confounding factor in trapping studies will likely depend on the numbers of pheromone-producing weevils captured and the elapsed time when weevils last fed prior to their capture in traps. Nonetheless, our results illustrate a previously unrecognized or disregarded occurrence which could provide a source of variation in pheromone trapping studies. As such, our findings suggest new trap or lure evaluations, when possible, should be conducted during periods when the opportunity to capture pheromone-producing weevils is minimized, such as before the initiation of square production in cotton or after harvest.