Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/5/2004
Publication Date: 6/14/2004
Citation: Spurgeon, D.W., Suh, C.P. 2004. Preliminary observations on the daily pattern of pheromone production by individual boll weevils. In: Proceedings of the Beltwide Cotton Conferences, January 5-9, 2004, San Antonio, Texas. 2004 CDROM. Interpretive Summary: The male boll weevil produces a mixture of chemicals (pheromone) that serves to attract other weevils of both sexes. Traps baited with this pheromone are an important part of programs to manage the boll weevil in cotton. Therefore, a better understanding of the factors controlling pheromone production by the weevil may help to improve the use of traps. We used new methods of measuring the amounts of pheromone produced by individual weevils to look at how pheromone production changes through the day, and how the time when weevils are fed affected this daily pattern. Weevils fed each morning (7:30 a.m.) produced more pheromone than weevils fed in the afternoon (3:30 p.m.). For both groups, most pheromone was produced between the time of 7:30 and 11:30 a.m., and 11:30 a.m. and 3:30 p.m. Considerable amounts of pheromone were also produced between 3:30 and 7:30 p.m. Pheromone production was lowest, but still substantial, between 7:30 p.m. and 7:30 a.m. (during the night). Weevils fed each morning produced more pheromone between 11:30 a.m. and 3:30 p.m. than weevils fed in the afternoon, but pheromone production by the two groups was more similar during the remainder of the day. Although we observed changes in pheromone production during the day, the changes were smaller than those previously reported. In particular, more pheromone was produced during the nighttime hours than was previously acknowledged. Our results provide insights not available in the literature, and suggest additional study could further improve our understanding of boll weevil pheromone production.
Technical Abstract: A sound understanding of the chemical ecology of the boll weevil, Anthonomus grandis Boheman, on cotton (Gossypium hirsutum L.) is important to efforts to improve pheromone trapping technologies. Recent reports of new methods of examining pheromone production by individual male weevils have indicated that most pheromone is not in the frass as was previously assumed. We used these new methods to evaluate the daily pattern of pheromone production of individual weevils, and the influence of time of food replacement on those patterns. Weevils fed daily at 0730 h (CDT) produced more pheromone (2.62 +/- 0.30 micrograms/h) than weevils fed at 1530 h (1.66 +/- 0.30 micrograms/h). Hourly pheromone production was highest during intervals of 0730 ' 1130 h (2.98 +/- 0.37 micrograms) and 1130 ' 1530 h (3.30 +/- 0.37 micrograms), intermediate between 1530 ' 1930 h (1.67+/- 0.31 micrograms), and lowest between 1930 ' 0730 h (0.58 +/- 0.16 micrograms). Weevils fed at 0730 h produced more pheromone during the 1130 ' 1530 h period than weevils fed at 1530 h, byt pheromone production by the two groups was more similar for other periods. Our results indicated less distinct daily patterns, and greater amounts of pheromone released during the scotophase, than were previously reported. Our results likely differ from the daily patterns of pheromone production occurring in the field because we did not simulate field temperatures. Still, they provide insights previously unavailable from the literature. These results also suggest additional study could further improve our understanding of the dynamics of boll weevil pheromone production.