Submitted to: Agricultural Research International Conference Proceedings
Publication Type: Research Notes
Publication Acceptance Date: 5/31/2002
Publication Date: N/A
Technical Abstract: Chemicals responsible for attraction of the Colorado potato beetle (CPB) Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) to its host plant and conspecifics have long been sought, since Mc Indoo in 1926  demonstrated the general attractiveness of potato plant volatiles to adult CPB. Only recently, I could identify several attracting volatiles that were emitted from potato plants and stimulated isolated antennae of CPB and its predators in coupled gas chromatography/ electroantennogram preparations [2,3]. Six artificial, mixtures of these components attracted adult CPB in laboratory behavioral tests. One of these artificial blends is attractive not only to adults of both sexes but also to larval forms , the first plant attractant for larval CPB. Thus, these blends may serve as attractants for food plants for all stages as well as for ovipositor sites for females. Further, together with colleagues, we also succeeded to finally identify a male-produced aggregation pheromone for the beetle . Since male beetles normally release only minor amounts of the pheromone, collection and chemical identification of it was only enabled after its release was enhanced nearly 200 fold by topical application of JH III and antennectomy. The pheromone surprisingly is (S)-3,7-dimethyl-2-oxo-oct-6-en-1, 3-diol, representing a novel structure for an insect pheromone. Antennal recepectors of both sexes respond selectively to the (S)-enantiomer; in laboratory behavioral bioassays, the (S)-enantiomer attracts both sexes while its antipode is inactive or might even be inhibitory. This investigation provides the first identification of pheromone for the CPB. Since it is produced by the males, our discovery is in contrast to the existing paradigm of a female-produced pheromone for this insect. Its role in the ecology of the beetle, however, has yet to be fully clarified. Furthermore, our findings show a positive influence of JH III on production and/or release of the pheromone and imply a control of pheromone release by antennal sensory input via a negative feedback loop, a new mechanism, only mentioned so far for the control boll weevil, Anthonomus grandis . The discovery of both insect and plant produced attractants for larval and adult CPB provides tools for use in alternative management strategies for pestiferous populations. Based on the results presented here and others from recent studies in my lab, the chemical basis of conspecific interactions and host plant selection is discussed.