Homofarnesals: female sex attractant pheromone components of the southern cowpea weevil, Callosobruchus chinensis.

The southern cowpea weevil, Callosobruchus chinensis (Coleoptera: Bruchidae), is a major pest of stored legumes in warm temperate and tropical climates. The female sex attractant pheromone was extracted from filter-paper shelters taken from containers that housed virgin females. The extracts were purified by various chromatographic techniques, and the biologically active components in the fractions were screened by gas chromatographic-electroantennographic detection analysis with male antennae. Two compounds that elicited electrophysiological responses were isolated, and gas chromatography-mass spectrometry, nuclear magnetic resonance, and micro-chemical analyses suggested that the active compounds were homofarnesals, (2Z,6E)- and (2E,6E)-7-ethyl-3,11-dimethyl-2,6,10-dodecatrienals. Males of C. chinensis were significantly attracted to filter paper discs loaded with the synthetic compounds at 0.01-0.1 ng compared to solvent control in a Y-tube olfactometer assay. These pheromone components represent unique chemical structures within the genus Callosobruchus.