|Webster, Francis - S.U.N.Y., SYRACUSE|
|Tang, Rong - S.U.N.Y., SYRACUSE|
Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 14, 1996
Publication Date: N/A
Interpretive Summary: The cowpea weevil (Callosobruchus maculatus), a serious pest of legumes worldwide, lacks an effective pheromone monitoring tool. We discovered the presence of five short-chain carbon acids that are individually attractive and when combined are additive. The compounds were evaluated in small chambers and in a wind tunnel and found to be excitatory and give an upwind flight response. In a related study with a different weevil pest of stored legumes, another new pheromone was discovered that was different from the cowpea weevil pheromone. These results are important to growers and processors of stored legumes as a new tool in integrated pest management programs.
Technical Abstract: The object of this study was to isolate and identify the female- produced sex pheromone of Callosobruchus maculatus. Volatiles were collected from virgin female beetles by adsorption on filter paper disks and solvent extraction. A bioassay tested the locomotory response of single males in glass vials. Crude extracts were subjected to column chromatography; all activity was confined to the methanol fraction indicating a polar compound. Acid-base partitioning of the crude extract isolated all activity in the acid fraction indicating that the pheromone was a carboxylic acid. The acids were identified by GC-MS and comparison with synthetic candidates: 3-methylene heptanoic acid, (Z)-3-methyl-3-heptenoic acid, (E)-3-methyl-3-heptenoic acid, (Z)-3-methyl-2-heptenoic acid, and (E)-3-methyl-2-heptenoic acid. Each synthetic acid was active individually to males and combinations had an additive effect. Upwind flight responses to the natural and synthetic pheromones were seen in a flight tunnel. (Z)-3-methyl-2-heptenoic acid, previously identified as the sex pheromone for C. analis, was inactive when compared to extracts of female volatiles. GC-MS analyses of C. analis volatiles revealed an unidentified C-8 acid with a GC retention time different from any of the C. maculatus acids.