Induction of Plant Volatiles by Herbivores with Different
Feeding Habits and the Effects of Induced Defenses
on Host-Plant Selection by Thrips
Casey M. Delphia
&
Mark C. Mescher
&
Consuelo M. De Moraes
Received: 11 September 2006 /Accepted: 23 February 2007 /
Published online: 29 March 2007
#
Springer Science + Business Media, LLC 2007
Abstract Induced plant responses to attack by chewing insects have been intensively
studied, but little is known about plant responses to nonchewing insects or to attack by
multiple herbivores with different feeding habits. We examined volatile emissions by
tobacco, Nicotiana tabacum, in response to feeding by the piercing–sucking insect western
flower thrips (WFT), Frankliniella occidentalis, the chewing herbivore Heliothis virescens,
and both herbivores simultaneously. In addition, we examined the effects of herbivore-
induced plant defenses on host-plant selection by WFT. Plants responded to thrips feeding
by consistently releasing five compounds. Simultaneous feeding by WFT and H. virescens
elicited the same 11 compounds emitted in response to caterpillar feeding alone; however,
two compounds, α-humulene and caryophyllene oxide, were produced in greater amounts
in response to simultaneous herbivory. In choice tests, thrips consistently preferred
uninduced plants over all other treatments and preferred plants damaged by caterpillars and
those treated with caterpillar saliva over those treated with caterpillar regurgitant. The
results are consistent with a previous finding that caterpillar regurgitant induces the release
of significantly more volatile nicotine than plants damaged by caterpillars or plants treated
with caterpillar saliva. A repellent effect of nicotine on WFT was confirmed by encircling
unwounded plants with septa releasing volatile nicotine. Our results provide the first direct
evidence that thrips feeding induces volatile responses and indicates that simultaneous
herbivory by insects with different feeding habits can alter volatile emissions. In addition,
the findings demonstrate that induced plant responses influence host-plant selection by
WFT and suggest that the induction of volatile nicotine may play a role in this process.
Keywords Plant–insect interactions
.
Induced defenses
.
Plant volatiles
.
Simultaneous herbivory
.
Ovipositional preference
.
Insect behavior
.
Host-plant selection
.
Frankliniella occidentalis
.
Heliothis virescens
.
Nicotiana tabacum
.
Nicotine
J Chem Ecol (2007) 33:997–1012
DOI 10.1007/s10886-007-9273-6
C. M. Delphia
:
M. C. Mescher
:
C. M. De Moraes (*)
Department of Entomology, The Pennsylvania State University,
535 ASI Building, University Park,
PA 16802, USA
e-mail: czd10@psu.edu