Submitted to: Proceedings of the Royal Society B
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/12/2013
Publication Date: 4/17/2013
Citation: Trona, F., Anfora, G., Balkenius, A., Knight, A.L., Tasin, M., Witzgall, P., Ignell, R. 2013. Neural ensemble coding merges sex and habitat chemosensory signals in an insect herbivore (RSPB-2012-2496). Proceedings of the Royal Society B. Vol 280, DOI 10.1098/rspb 2013.0267. Interpretive Summary: Codling moth is the major insect pest attacking apple in the United States and is an important quarantine pest. ARS researchers at the USDA, ARS, Yakima Agricultural Research Laboratory, Wapato, WA in collaboration with researchers at IASMA Research and Innovation Center, S. Michele, Italy and Swedish Agricultural University, Alnarp, Sweden are studing the integration of sex and host plant chemical signals in the olfaction system in codling moth. Behavioral assays combined with visual imaging of the antennal lobe show that blends of sex pheromone and host plant volatiles can interact synergistically to enhance the response of male moths to their sex pheromone. Results suggest that new chemical blends can be developed to improve both monitoring and control through mating disruption of codling moth.
Technical Abstract: We used a neuroethological approach to study how blends of the main sex pheromone compound, codlemone, and three host plant volatiles, butyl hexanoate, ß-farnesene and pear ester, affect odor processing and ensuing behavior in the codling moth Cydia pomonella. In wind tunnel bioassays, a higher proportion of male moths made close upwind flights and contact with the source of blends of pheromone and plant volatiles than to the single compounds alone. Calcium imaging of the primary olfactory centre, the antennal lobe (AL) showed that the presence of plant volatiles enhanced the response to a sub-threshold dose of codlemone in the cumulus, the large pheromone-tuned glomerulus, while additive and suppressive interactions were observed in other parts of the AL. Intracellular recordings from AL projection neurons confirmed that synergistic responses were confined to the cumulus and other glomeruli in the macroglomerular complex. Hence, we show that behaviorally active blends of sex pheromone and host plant volatiles elicit a strong synergistic effect in the pheromone subsystem of the codling moth AL. Our physiological analysis demonstrates that the coding of odor signals from conspecifics and plants is highly integrated in the central nervous system. This highlights the role of host plant cues in premating sexual communication and re-emphasizes that, in nature, sex signals and habitat cues are always perceived as an ensemble.