Olfactory recognition of host plants in the absence of host-specific volatile compounds: Host location in the black bean aphid, Aphis fabae.

The black bean aphid, Aphis fabae, responds behaviorally to the odor of its host plant faba bean (Vicia faba) in olfactometer bioassays by spending more time in the treated than control regions. We have shown previously that a blend of fifteen volatile compounds emitted by V. faba elicits the same response as a headspace sample of an intact V. faba plant. Here we report that no single compound within this blend fully accounts for the behavioral response and that the responses to individual compounds are different when in the context of the blend. As none of the compounds are specific to the host, we have hypothesized that A. fabae responds preferentially to the blend of compounds when presented in a species-specific combination of volatiles or in ratios specific to V. faba. Future plans to test which of these two hypotheses pertains to host-seeking Aphis fabae are discussed.