Ozone-driven degradation of sex pheromone in Plutella xylostella: Implications for reproductive communication and mating success

Abstract

Insect sex pheromones are essential for mate recognition and reproductive success. In Lepidoptera, the most abundant sex pheromonal compounds are C10-C18 unsaturated straight-chain acetates, alcohols, or aldehydes. However, their chemical structures make them susceptible to degradation by atmospheric oxidants. Here, we investigated the impact of exposure to ozone (O3), an important air pollutant, on the composition and attractiveness of the sex pheromone of the diamondback moth (DBM) Plutella xylostella. The gland extracts revealed that the P. xylostella sex pheromone comprises three components, (Z)-11-hexadecenal, (Z)-11-hexadecen-1-ol, and (Z)-11-hexadecenyl acetate. All three components, both alone and when mixed as a synthetic pheromone blend, decreased significantly in O3-enriched air. The relative ratio of the pheromonal compounds was also altered following exposure to moderate (40 ppb) and high (80–120 ppb) O3 concentrations. These chemical changes were associated with altered behavior of male moths in dual-choice assays. Males appeared unable to discriminate between pheromone extract and hexane in O3-enriched air, even at moderate concentrations. Moreover, males orientated toward clean air-exposed pheromone over O3-exposed pheromone. Gas chromatography-mass spectrometry (GC-MS) analyses of pheromone gland extracts from virgin females exposed to O3, showed a decrease in the amounts of the three pheromone components and an altered blend ratio as the O3 concentration increased. These findings demonstrate that O3 pollution can disrupt sexual communication in P. xylostella, even at current tropospheric concentrations. With the conserved chemical characteristics of moth pheromones, these results suggest general implications to insect reproduction and the efficacy of pheromone-based pest control under polluted atmospheric conditions.