MONITORING PHEROMONE PRODUCTION OF INDIVIDUAL BOLL WEEVILS

Authors: Spurgeon, Dale; Marshall, Henry

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/8/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Male boll weevils attract other boll weevils by releasing a specific mixture of chemicals called pheromone. Traps baited with man-made chemicals that imitate the natural pheromone are critically important in efforts to detect and monitor weevil populations in management programs. However, factors affecting the amount of pheromone male weevils can produce eare poorly understood. Improved understanding of these factors could lead to development of more effective trap lures and improved trapping schemes. Most studies of boll weevil pheromone production have assumed that most or all of the pheromone is present in the droppings of the male weevil. We developed a system of measuring the pheromone in the air surrounding the weevil (headspace) in addition to that in the droppings. Our system of pheromone measurement recovered known amounts of pheromone with about 95% efficiency. Measurements of pheromone in the droppings were similar to those reported by other investigators. However, we found that most of the pheromone produced was in the headspace, and that weevils were capable of producing a much larger amount of pheromone that is generally recognized. Further, using our techniques, we found that weevils were capable of producing pheromone at earlier ages than were previously reported. Our techniques appear suitable for measuring pheromone production by individual weevils and should be valuable in further efforts to understand the factors controlling pheromone production.

Technical Abstract: The boll weevil pheromone trap is a critically important tool in boll weevil population monitoring and management, but much remains to be learned regarding the factors influencing pheromone production by male weevils and their repercussions to trapping efforts. Standard methods of measuring boll weevil pheromone production rely on relatively large groups of weevils sand assume that most or all of the pheromone produced is present in the frass. We devised and evaluated a technique to monitor pheromone production by individual weevils, using an adsorbent to collect pheromone from the air around the weevil (headspace). Pheromone recovery efficiency of the method was about 95%. Pheromone production indicated by frass extractions was similar to that in previous reports. However, measurements of pheromone from the headspace indicated that pheromone in the frass represents a small fraction of the total pheromone produced, and that the boll weevil can produce a much larger amount of pheromone than wa previously recognized. In addition, use of our technique allowed detection of pheromone production at an earlier weevil age than is typically reported. Our techniques appear uniquely suitable for monitoring boll weevil pheromone production and should prove invaluable to further efforts to investigate the ecology and management implications of boll weevil pheromone production.