Journal of Chemical Ecology (2003) 29, 145-162

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Sandrine Gouinguené, Hans Alborn and Ted C.J. Turlings (2003)
Induction of volatile emissions in maize by different larval instars of Spodoptera littoralis
Journal of Chemical Ecology 29 (1), 145-162
Abstract: Maize plants under attack by caterpillars emit a specific blend of volatiles that is highly attractive to parasitic wasps. The release of these signals is induced by elicitors in the caterpillar regurgitant. Studies suggest that plants respond differently to different herbivore species and even to different herbivore stages, thus providing parasitoids and predators with specific signals. We tested if this is the case for different larval instars of the noctuid moth Spodoptera littoralis when they feed on maize plants. Cut maize plants were incubated in diluted regurgitant from second, third, or fifth instar caterpillars. There were no differences in total amount released after these treatments, but there were small differences in the release of the minor compounds phenethyl acetate and alpha-humulene. Regurgitant of all three instars contained the elicitor volicitin. To test the effect of actual feeding by the larvae, potted plants were infested with caterpillars of one of the three instars, and volatiles were collected the following day. The intensity of the emissions was correlated with the number of larvae feeding on a plant, and with the amount of damage inflicted, but was independent of the instar that caused the damage. We also used artificial damage to mimic the manner of feeding of each instar to test the importance of physical aspects of damages for the odor emission. The emission was highly variable, but no differences were found among the different types of damage. In olfactometer tests, Microplitis rufiventris, a parasitoid that can only successfully parasitize second and early third instar S. littoralis, did not differentiate among the odors of maize plants attacked by different instar larvae. The odor analyses as well as the parasitoid's responses indicate that maize odors induced by S. littoralis provide parasitoids with poor information on the larval developmental stage. We discuss the results in the context of variability and lack of specificity in odorous plant signals.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Ted C.J. Turlings

Research topic(s) for pests/diseases/weeds:
environment - cropping system/rotation
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
environment/habitat manipulation
general biology - morphology - evolution

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Spodoptera littoralis Maize/corn (Zea mays)
Microplitis rufiventris (parasitoid) Spodoptera littoralis