Floral Cure-All

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Science  21 Jan 2011:
Vol. 331, Issue 6015, pp. 264
DOI: 10.1126/science.331.6015.264-b

A traditional Chinese medicine, Shih-chun-tze, used to treat infections with the large parasitic nematode Ascaris has as its active ingredient l-quisqualic acid, a known but rare agonist of excitatory amino acids. Unexpectedly, when Ranger et al. were looking for explanations for the well-known phenomenon of Japanese beetle (Popilia japonica) paralysis, they found this agonist in the flowers of ornamental pelargoniums (zonal geraniums). Ingestion causes the beetles to be paralyzed for several hours, increasing their vulnerability to predation, desiccation, and lost reproduction. The beetles find the petals irresistible, however, because after recovery they come back for more. Japanese beetle damage costs horticulture hundreds of millions of dollars annually, but since the zonal geranium phenomenon was first described in the 1920s, the paralytic agent had not been identified. Silica gel flash chromatography was used to characterize the active ingredients in petals, and the active components were tested in agar plugs fed to beetles. Consumption of about 5 ng of l-quisqualic acid (thought to mimic the neurotransmitter l-glutamic acid), equivalent to one or two petals, is sufficient to paralyze the beetles. The work indicates that zonal geraniums may be a promising natural source of a novel pest control agent.

Proc. Natl. Acad. Sci. U.S.A. 108, 10.1073/pnas.1013497108 (2011).

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