Key microbial odorants for innovative codling moth control

Phytophagous insects typically feed on only a few plants and shifts to new hosts promote speciation and biodiversity. Host plant finding depends on olfactory cues.

It is, however, yet unknown which chemicals encode specific host recognition and attraction.Our scope is to identify the olfactory receptors (ORs), and their cognate ligands that mediate host finding in codling moth, a specialist feeder and the economically most important pest insect on apple.

Plant endophytic microbes that are part of the codling moth larval diet produce a wealth of volatiles - but their role in host plant finding is yet unknown.Some microbial metabolites are species-specific, and they are released in small amounts, together with many abundant and ubiquitous plant volatiles.

We therefore use single ORs, expressed in Drosophila melanogaster antennal neurons, for high-resolution headspace screening.We found that one key codling moth OR is tuned to pear ester, a strong bisexual host plant attractant, which is produced by endophytic yeasts.

Further, highly expressed codling moth ORs are seemingly also tuned to yeast metabolites, leading us to ask whether host plant recognition is mediated by plant endophytic microbes.A key motive for pursueing this work is to develop lures for pest insects, especially for egg-laying females, which would become valuable tools for sustainable management.The expected results are of general significance and applicable to other insects.