A novel attractant for Anastrepha ludens (Diptera: Tephritidae) from a Concord grape product

An attractant for Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), was developed from a commercial product called Sabor Uva containing processed Concord grape juice. The principal volatile components of Sabor Uva aroma were identified and an aqueous mixture of 15 components that was gas chromatographically similar to Sabor Uva was prepared. This mixture was equivalent to Sabor Uva in attractiveness by using wind-tunnel bioassays. After deleting chemicals that did not contribute to attractiveness, and increasing the concentrations of the remaining chemicals, the final attractant contained propylene glycol (90,000 ppm, vol/vol), acetic acid (4500), methyl anthranilate (1800), ethyl 2-methylpropionate (670), and one or both of the esters ethyl 3-methylbutyrate (44) and 2-methylbutyl propionate (44), in aqueous solution. This mixture was approximately 1.8X as attractive as Sabor Uva by indirect comparison. Deletion of propylene glycol, acetic acid, methyl anthranilate, or ethyl 2-methylpropionate from the mixture significantly decreased attractiveness. Deletion of either of the other two esters seemed to diminish attractiveness although effects were not statistically significant. Deletion of water from the mixture significantly decreased attractiveness. We conclude that propylene glycol, acetic acid, methyl anthranilate, water, and at least one or as many as all three of the methyl-branched esters are essential for complete attractiveness.