A Male-produced Aggregation Pheromone Blend Consisting of Alkanediols,Terpenoids, and an Aromatic Alcohol from the Cerambycid Beetle Megacyllene caryae

Bioassays conducted with a Y-tube olfactometer provided evidence that both sexes of the cerambycid beetle Megacyllene caryae (Gahan) were attracted to odor produced by males. Odor collected from male M. caryae contained eight male-specific compounds: a 10:1 blend of (2S,3R)- and (2R,3S)-2,3-hexanediols (representing 3.2 ± 1.3% of the total male-specific compounds), (S)-(−)-limonene (3.1 ± 1.7%), 2-phenylethanol (8.0 ± 2.4%), (−)-α-terpineol (10.0 ± 2.8%), nerol (2.1 ± 1.5%), neral (63.3 ± 7.3%), and geranial (8.8 ± 2.4%). Initial field bioassays determined that none of these compounds was attractive as a single component. Further field trials that used a subtractive bioassay strategy determined that both sexes were attracted to the complete blend of synthetic components, but the elimination of any one component resulted in a decline in trap captures. Blends that were missing (2S,3R)-2,3-hexanediol, (2R,3S)-2,3-hexanediol, or citral (a 1:1 mixture of neral and geranial) attracted no more beetles than did controls. A pheromone blend of this complexity, composed of alkanediols, terpenoids, and aromatic alcohols, is unprecedented for cerambycid species.