CONTINUATION OF PHEROMONE PRODUCTION BY BOLL WEEVILS FOLLOWING HOST REMOVAL

Authors: Suh, Charles; Spurgeon, Dale

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/5/2004
Publication Date: 6/14/2004
Citation: Suh, C.P., Spurgeon, D.W. 2004. Continuation of pheromone production by boll weevils following host removal. In: Proceedings of the Beltwide Cotton Conferences, January 5-9, 2004, San Antonio, Texas. 2004 CDROM.

Interpretive Summary: Recent observations suggested that some boll weevils captured in traps may continue to release a chemical (pheromone) that attracts other weevils to the traps. This previously unrecognized occurrence could effectively bias the results of trapping studies, particularly those involving comparisons of new trap designs or pheromone lures. Although it is universally accepted that weevils require access to food to produce pheromone, continuation of pheromone release following isolation from food, as would be the case if a weevil was captured in a trap, has not been documented. We examined pheromone production in weevils following their isolation from food, and found that weevils continued to release pheromone for at least two days. Although pheromone production declined substantially following food removal, weevils still produced pheromone amounts sufficient to attract other weevils. Consequently, our findings accentuate the need to conduct trap or lure evaluations during periods when the opportunity to capture pheromone-producing weevils is minimized.

Technical Abstract: Comprehensive knowledge of the chemical ecology of the boll weevil, especially with regard to the production of and response to pheromone, is critically important to continued efforts to improve pheromone traps, lures, and the interpretations of trapping data. In light of recent reports demonstrating a strong correlation between weevil accessory gland condition and pheromone production, existing dissection data from trapping studies implied that at least some trap-captured weevils were capable of continued pheromone release. Thus, the possibility of weevils continuing to release pheromone in traps was investigated by monitoring pheromone production by individual weevils following their removal from food. Pheromone production during the 24-h collection period immediately prior to food removal averaged 46 micrograms. Of the 13 pheromone producing weevils, 12 weevils continued to release pheromone during first 24-h starvation period, but the average pheromone production level during this period dropped to 10 micrograms. During the second day of starvation, only 5 weevils continued to release pheromone and average daily pheromone production was reduced to 3 micrograms. In comparison, daily pheromone production by weevils with continued access to food varied little throughout the study period. These results clearly demonstrate that pheromone-producing weevils continued to release pheromone in the absence of a host. This previously unrecognized capability could represent an important source of variation in trapping studies, particularly in those involving comparisons of traps or lures.