CHEMOECOLOGY

, Volume 12, Issue 1, pp 1–10

The roles of nicotine and natural enemies in determining larval feeding site distributions of Manduca sexta L. and Manduca quinquemaculata (Haworth) on tobacco

  • Karen M. Kester
  • Steven C. Peterson
  • Frank Hanson
  • D. Michael Jackson
  • R. F. Severson
Article

DOI: 10.1007/s00049-002-8320-6

Cite this article as:
Kester, K., Peterson, S., Hanson, F. et al. Chemoecology (2002) 12: 1. doi:10.1007/s00049-002-8320-6

Summary

Field observations indicated that hornworms select feeding sites non-randomly on tobacco. We tested the hypotheses that differences in feeding site locations of larvae of Manducasexta L. and Manducaquinquemaculata (Haworth) (Lepidoptera: Sphingidae) on tobacco could be explained by differential nicotine concentrations within plants and leaves, species-specific responses to nicotine, or pressure exerted by natural enemies. Results showed that third-instar larvae of M. sexta fed more proximally and centrally on the leaf, whereas M. quinquemaculata fed more distally. Within-plant selection of leaves did not differ; both species selected leaves in the middle region of the plant. Nicotine concentrations in a high nicotine genotype, NC95, varied within each leaf, increasing 2—3 fold from the basal to apical portion of the leaf, and within each plant, increasing 7—10 fold from the first fully expanded leaf to the twelfth (lowest) leaf. In laboratory bioassays, both Manduca species responded to nicotine as a feeding deterrent. Electrophysiological studies demonstrated that gustatory organs of both species responded to nicotine at concentrations found in tobacco leaves and that M. quinquemaculata generally showed a less vigorous response to nicotine than M. sexta. Field mortality of M. sexta due to parasitism by Cotesiacongregata (Say) and to parasitism and predation combined differed among feeding sites; predation alone did not. Results suggest that although nicotine concentration and species specific responses to nicotine play a role in determining feeding site locations, pressure exerted by natural enemies, especially parasitism by C. congregata, is more important.

Key words

Feeding behavior tritrophic interactions chemoreception electrophysiology nicotine tobacco Lepidoptera: Sphingidae Manduca Manduca sexta Cotesia congregata 

Copyright information

© Birkhäuser Verlag 2002

Authors and Affiliations

  • Karen M. Kester
    • 1
  • Steven C. Peterson
    • 2
  • Frank Hanson
    • 2
  • D. Michael Jackson
    • 3
  • R. F. Severson
    • 4
  1. 1.Department of Biology, Virginia Commonwealth University, 1000 W. Cary St., Richmond, VA 23284-2012, USAUSA
  2. 2.Department of Biological Sciences, University of Maryland, Baltimore, Maryland 21228, USAUSA
  3. 3.USDA-ARS, U.S. Vegetable Laboratory, 2875 Savannah Hwy, Charleston, SC 29414, USAUSA
  4. 4.USDA-ARS, Tobacco Safety Research Unit, Athens, Georgia 30604, USAUSA