D3269: Codling moth Cydia pomonella chemical ecology

Behaviour-modifying chemicals mediate sexual communication and host choice in insect herbivores. Sex pheromones are believed to attract insects and especially moths all by themselves, although, in a natural environment, pheromones are not perceived in isolation, since they are released into an atmosphere of plant odorants.
The larva of codling moth is the worm that feeds in apple and orchard air permeation with female sex pheromone is used worldwide to disrupt mate finding, for environmentally safe population control. We show for the first time that codling moth pheromone is efficient for male attraction only in the presence of host plant odour. In non-host vegetation, male attraction to sex pheromone was very strongly reduced.
The role of host odour in sex attraction was substantiated by blending synthetic pheromone, codlemone, and the kairomone pear ester, a strong host plant attractant. An admixture of pear ester entirely rescued pheromone attraction in non-host vegetation.
Our field behavioural assay substantiates that host plant olfactory cues are integral part of sexual communication and mate recognition, which provides a mechanism for how shifts to new host plants produce new mate recognition signals.
Perception of pheromone and kairomone depends on olfactory receptors and neural circuits that are experimentally tractable. Taxonomically related species, some of which share plant hosts or pheromones, invite investigations of olfactory receptor ligands and phylogeny.
A practical implication concerns insect control with pheromones. Codling moth mating disruption is inefficient at high population densities, since synthetic pheromone released into an orchard atmosphere intensifies male mate finding behaviour.