Response of females to a novel pheromone produced by male Diaprepes root weevils (Diaprepes abbreviatus)

Diaprepes abbreviatus is a neotropical weevil whose larvae feed on the roots of a wide range of economically important host plants. First introduced into Florida in the 1960s, it has appeared in California, Louisiana and Texas, and now threatens Mexico, Central and South America. An unsaturated hydroxy ester pheromone collected from the headspace and feces of male D. abbreviatus, has been isolated, identified and synthesized. The pheromone, methyl (E)-3-(2-hydroxyethyl)-4-methyl-2-pentenoate, was discovered by gas chromatography-coupled electroantennogram detection (GC-EAD) and identified by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR). The activity of the synthetic E isomer was confirmed by GC-EAD, GC-MS, NMR and behavioral assays. In a two-choice olfactometer bioassay, female D. abbreviatus moved upwind towards the synthetic pheromone or a source of natural pheromone (male frass) more often compared with clean air. In olfactometer assays, males showed no clear preference for the synthetic pheromone alone. This compound, alone or in combination with plant volatiles, may play an important role in orientation by D. abbreviatus to conspecifics. A second putative pheromone has been identified from the frass of males and females and elicits antennal responses from both sexes. Ongoing effort focuses on description of behavioral response of males and females to single compounds and blends of pheromones and kairomones.