Journal of Chemical Ecology

, Volume 24, Issue 9, pp 1529-1549

First online:

Biological Activity of Datura wrightii Glandular Trichome Exudate Against Manduca Sexta Larvae

  • Nicole M. Van DamAffiliated withDepartment of Entomology, University of California, Riverside, Riverside
  • , J. Daniel HareAffiliated withDepartment of Entomology, University of California, Riverside, Riverside

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Natural populations of Datura wrightii in southern California consist of two distinctly different phenotypes. The leaves of one phenotype are densely covered with nonglandular trichomes and feel velvety. The other phenotype is covered with larger type IV glandular trichomes that excrete a sticky exudate. Neonate larvae of M. sexta reared on velvety leaves developed significantly faster than larvae on sticky leaves. Larvae on sticky leaves took 28% longer to reach the prepupal stage. Survival and pupal weight were not significantly different between the two groups. First instars of M. sexta had a significantly higher consumption rate on velvety leaves than on sticky leaves. Removal of the exudate from stickly leaves significantly increased larval consumption rates compared to unwashed controls. Female moths did not show an oviposition preference; both in the lab and in the field the two trichome phenotypes of D. wrightii received similar egg loads. Because there were no significant differences in other nutritional factors between the two plant phenotypes, we concluded that the exudate was responsible for the effect. We isolated a complex mixture of sugar esters (SE) as the biologically active compounds in the exudate of D. wrightii. The SE mixture was composed of glucose esterified with several combinations of straight chain C6–C9 acids. By comparing GC-MS spectra of synthetic SE with the SE extracted from D. wrightii, we identified one of the SE as 3′-O-hexanoyl glucose.

Tobacco hornworm Solanaceae insect–plant interactions glandular trichomes exudate resistance polymorphism oviposition choice acyl sugar esters Lepidoptera Sphingidae