Reidentification of the female sex pheromone of the Indian meal moth, Plodia interpunctella: evidence for a four-component pheromone blend

Pheromone gland extracts from calling female Plodia interpunctella containe d at least seven compounds that consistently elicited electroantennographic responses from male antennae upon gas chromatographic analysis. Three of t hese compounds were found to be the previously identified gland constituent s, i.e., (Z,E)-9,12-tetradecadienyl acetate (Z9,E12-14:OAc), (Z,E)-9,12-tet radecadienal (Z9,E12-14:Ald) and (Z,E)-9,12-tetradecadienol (Z9,E12-14:OH). A fourth EAD-active compound was identified as (Z)-9-tetradecenyl acetate (Z9-14:OAc). The homologue (Z)-11-hexadecenyl acetate (Z11-16:OAc) was also identified in the extracts, but showed no EAD activity. The identity of al l five compounds was confirmed by comparison of GC retention times and mass spectra with those of synthetic standards. In flight tunnel tests there we re no significant differences in response of male P. interpunctella to the bait containing all four EAD-active compounds and the responses to female g land extacts. A behavioural assay of different two-compound blends in the f light tunnel showed that only addition of the corresponding aldehyde to the major pheromone component Z9,E12-14:OAc raised the male response. A subtra ctive assay, however, revealed that the exclusion of any of the compounds f rom the complete four-compound blend reduced its activity significantly. We thus conclude that the female-produced sex pheromone of P. interpunctella consists of at least four components, i.e., Z9,E12-14:OAc, Z9,E12-14:Ald, Z 9,E12-14:OH and Z9-14:OAc. In a field trapping test performed in a storage facility, the four-componen t blend attracted significantly more males of P. interpunctella than traps baited with Z9,E12-14:OAc alone. In contrast, the highest number of Ephesti a kuehniella males was found in the traps baited with this major component, suggesting that the secondary pheromone components contribute to the speci es specificity of the blend.