Submitted to: Journal of Entomological Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/27/2006
Publication Date: 4/15/2007
Citation: Spurgeon, D.W., Suh, C.P. 2007. Diel patterns of pheromone production in the boll weevil (Coleoptera: Curculionidae). Journal of Entomological Science. 42:250-260. Interpretive Summary: The male boll weevil communicates chemically with other male and female weevils by giving off a mixture of four specific chemicals (pheromone). Detailed knowledge of these chemical communications is needed to improve trapping methods. In laboratory studies of pheromone production during four daily periods (7:30-11:30 AM, 11:30 AM-3:30 PM, 3:30-7:30 PM, and 7:30 PM-7:30 AM), we found that weevils fed daily at 7:30 AM produced more pheromone than weevils fed at 3:30 PM, and 11-d-old weevils produced more pheromone than 9-d-old weevils. Weevils fed at 7:30 AM produced pheromone in a distinct daily pattern with a peak in production between 11:30 AM-3:30 PM and least production at night, and the composition of the pheromone was similar among different periods. Weevils fed at 3:30 PM also produced pheromone in a daily pattern, but that pattern was less distinct and composition of the pheromone changed throughout the day. Our results demonstrate a true daily periodicity in pheromone production by the boll weevil similar to previously observed daily patterns in trap response, and show that careful control of weevil diets is essential to accurate results in such studies.
Technical Abstract: Detailed knowledge of boll weevil, Anthonomus grandis Boheman, chemical ecology on cotton, Gossypium hirsutum L., is needed to improve pheromone trapping methods. Recent studies using headspace collections have indicated that most pheromone is not in the feces as previously assumed. We used headspace collections to examine the diel patterns of boll weevil pheromone production and to determine whether the timing of food replacement influenced those patterns. Pheromone production of individual 9- and 11-d-old weevils was estimated during four daily periods (0730-1130, 1130-1530, 1530-1930, and 1930-0730 h CDT) under temperatures of 27°C and with a 13:11 (L:D) h photoperiod. Weevils fed daily at 0730 h produced more pheromone (2.83 microgram/h) than weevils fed at 1530 h (1.95 microgram/h), and 11-d-old weevils produced more pheromone (2.62 microgram/h) than 9-d-old weevils (2.16 microgram/h). Furthermore, weevils fed at 0730 h exhibited a clear diel pattern of pheromone production with maximal and minimal production occurring between 1130-1530 h and 1930-0730 h, respectively. Weevils fed at 1530 h exhibited a similar periodicity, but the pattern was less distinct. Pheromone composition of weevils fed at 0730 h was relatively consistent among daily periods and the ratio of the four components was approximately 45:42:3:10 (I:II:III:IV). However, pheromone composition varied significantly among daily periods for weevils fed at 1530 h. Our results demonstrate a diel periodicity in pheromone production by the boll weevil, and illustrate the need for careful control of weevil diets in such studies.