Aggregation pheromone of the agave weevil, Scyphophorus acupunctatus

The agave weevil, Scyphophorus acupunctatus Gyllenhal (Coleoptera: Curculionidae), is the most important insect pest of wild and cultivated agaves in the world. Combined gas chromatography-electroantennography (GC-EAD) analysis of male volatile extracts showed that four peaks elicited antennal responses from males and females. The peaks were identified by GC-mass spectrometry (GC-MS) as 2-methyl-4-heptanol (1), 2-methyl-4-octanol (2), 2-methyl-4-heptanone (3), and 2-methyl-4-octanone (4). Electroantennogram (EAG) recordings of both sexes to 0.01-, 0.1-, 1-, and 10-mu g stimulus load of synthetic compounds showed that the dose of the tested compounds and weevil sex significantly influenced the antennal response of S. acupunctatus. However, there was no sexual dimorphism in the antennal responses to the four synthetic compounds evaluated because the EAG profiles revealed no interaction between doses by sex. Antennae of S. acupunctatus were most sensitive to compounds 2 and 4, reaching the threshold at a 0.01-mu g stimulus load. Weevil antennae were less sensitive to compounds 1 and 3, and the threshold response to these compounds was 0.1 mu g. Behavioural evaluation of the synthetic compounds showed them to be attractive to both males and females in a Y-tube olfactometer. Field experiments confirmed the laboratory results, showing that all components, singly or in blends, were attractive to the weevils. In general, traps baited with the quaternary blend of compounds 1-4 captured significantly more weevils than traps baited with males. However, compounds 3 and 4 were sufficient to obtain captures equivalent to those by the quaternary blend. The potential use of the aggregation pheromone in the development of a mass-trapping programme as a viable pest management alternative for S. acupunctatus is discussed.