C. dactylon (center) showing BGWL symptoms.

Biol. Lett. (2010) 6, 314–317 doi:10.1098/rsbl.2009.0953 Published online 23 December 2009

Is quality more important than quantity? Insect behavioural responses to changes in a volatile blend after stemborer oviposition on an African grass

Toby J. A. Bruce1, Charles A. O. Midega2, Michael A. Birkett1, John A. Pickett1,* and Zeyaur R. Khan2

1. Rothamsted Research, Harpenden, Herts AL5 2JQ, UK
2. International Centre of Insect Physiology and Ecology (icipe), PO Box 30772, Nairobi, Kenya *Author for correspondence ( This e-mail address is being protected from spambots. You need JavaScript enabled to view it ).

Abstract

Plants subjected to insect attack usually increase volatile emission which attracts natural enemies and repels further herbivore colonization. Less is known about the capacity of herbivores to sup- press volatiles and the multitrophic consequences thereof. In our study, the African forage grass, Brachiaria brizantha, was exposed to ovipositing spotted stemborer, Chilo partellus, moths. A marked reduction in emission of the main volatile,     (Z )-3-hexenyl      acetate   (Z3HA), occurred following oviposition but the ratio of certain other minor component volatiles to Z3HA was increased. While further herbivore colonization was reduced on plants after ovipos- ition, the new volatile profile caused increased attraction of an adapted parasitoid, Cotesia sesamiae. Our results show that insect responses are dependent on the quality of volatile emis- sion rather than merely the quantity in this multitrophic interaction.