Submitted to: Journal of Chemical Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/24/2005
Publication Date: 4/12/2006
Citation: Bartelt, R.J., Cosse, A.A., Zilkowski, B.W., Weisleder, D., Grode, S.H., Wiedenmann, R.N., Post, S.L. 2006. Dimethylfuran-lactone pheromone from males of Galerucella calmariensis and Galerucella pusilla (Coleoptera: Chrysomelidae). Journal of Chemical Ecology 32(3):693-712. Interpretive Summary: Galerucella calmariensis and G. pusilla are small brownish "leaf" beetles that have been introduced into the U.S. from Europe as biological control agents for the invasive wetland weed, purple loosestrife. One challenge in biocontrol programs is to understand population trends after the agents have been released into new areas, such as dispersal rates, seasonal timing, and abundance over time. Traps baited with the beetle’s pheromone would provide a sensitive and selective means for acquiring such information. The pheromones of these species were not known, however, so a project was undertaken to gain such information. One compound was discovered that is emitted only from the male beetles (surprisingly, in both species) and that is sensitively detected by the antennae of both sexes, two properties consistent with a male-produced aggregation pheromone. The beetle compound was chemically analyzed and found to have a novel structure, which contains two rings (one a furan and the other a lactone). Analysis was difficult because of the minute amount of material available. Once the structure was known, the compound was synthesized in the laboratory. The compound was tested in traps in northeastern Illinois during May of 2005, and it was found to be attractive to both the males and females of both species. This research will be of basic interest to entomologists involved with this species, to scientists working with pheromones in general, and to chemists specializing in natural products. Research will continue on the development of the pheromone as a practical tool in the biocontrol of purple loosestrife.
Technical Abstract: Males of Galerucella calmariensis and G. pusilla (Coleoptera: Chrysomelidae) emit a pheromonally active compound while feeding on host foliage. Isolation of the compound from collected volatiles was guided by male/female comparisons of gas chromatograms and by GC-EAD. It was identified by EI, CI, and HR mass spectrometry; NMR and UV spectroscopy; and microchemical tests as the novel dimethylfuran lactone, 12,13-dimethyl-5,14-dioxa-bicyclo[9.2.1]tetradeca-1(13),11-dien-4-one. The structure was confirmed by synthesis, and the synthetic compound was attractive in the field to the males and females of both species. These beetles were previously introduced into North America as biological control agents for the invasive wetland weed, purple loosestrife Lythrum salicaria, and the pheromone could become a tool for monitoring populations. A new method is described for distinguishing the two species, based on the tibial spurs of the males.