Submitted to: Environmental Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/18/2002
Publication Date: 2/1/2003
Citation: SPURGEON, D.W. AGE DEPENDENCE OF PHEROMONE PRODUCTION BY THE BOLL WEEVIL (COLEOPTERA: CURCULIONIDAE). ENVIRONMENTAL ENTOMOLOGY. 2003. 32(1):31-38. Interpretive Summary: The boll weevil pheromone is a mixture of four chemicals that is produced by the male and is attractive to both sexes. The factors affecting pheromone production have been extensively studied, but previous methods assumed that most or all of the pheromone was in the feces of the weevils. However, our study revealed that about 95% of the total pheromone produced was recovered from the air surrounding the weevil while only 5% was recovered from the feces. The amount of pheromone produced by the weevils increased each day until weevils were about 9 days old. Also, the ratios of the four chemical components changed for the first few days of adult life and then became more stable. High levels of pheromone production occurred when the specialized (accessory) glands of the male were large, while weevils with small accessory glands produced little or no pheromone. These results provide improved estimates of the amounts of pheromone that boll weevils can produce. This information will be useful in future studies to better understand how the boll weevil finds and colonizes the cotton crop, and in interpreting population data provided by pheromone-baited traps.
Technical Abstract: Factors influencing pheromone production by the boll weevil, Anthonomus grandis Boheman, have been extensively studied, yet recent research utilizing new methods suggests much remains unknown in this regard. The studies reported herein examined age-related changes in production and composition of pheromone at ages from 0 - 6 d, and at 3, 6, 9, and 12 d, respectively, and evaluated the association between accessory gland condition and pheromone production. Estimates of pheromone from extracted feces were near the upper values previously reported. However, ~95% of the total pheromone was obtained from headspace collections. Based on feces extractions, pheromone production increased with age until the sixth day, while headspace collections indicated an increase in production until the ninth day of adulthood. The boll weevil pheromone is composed of two alcohols (components I and II) and two aldehydes (components III and IV), and ratios of these components changed with age. Component I was dominant for the first days of adult life, but the composition subsequently stabilized at about 42.5 : 42.5 : 5 : 10 (I:II:III:IV). Also, high levels of pheromone production were associated with well developed accessory glands, while weevils with small, transparent glands produced little or no pheromone. These results demonstrate production of pheromone in greater quantities, and at earlier ages, than was previously recognized. Additional study using the methods reported herein should provide improved understanding of the dynamics of boll weevil pheromone production that will facilitate ecological interpretation of field data and improvements in trapping systems.