Effects of minor pheromone components on orientation behavior and mating decision‐making strategy in <i>Micromelalopha sieversi</i>

Micromelalopha sieversi (Staudinger) (Lepidoptera: Notodontidae) is a destructive defoliator of poplar (Populus sp.) trees in China. In prior study, (13Z,15E)-octadeca-13,15-dienal (Z13,E15-18:Ald) (I) and (13Z,15Z)-octadeca-13,15-dienal (Z13,Z15-18:Ald) (II) were identified from the sex pheromone glands of M. sieversi females. Although traps baited with Z13,E15-18:Ald (I) captured M. sieversi males, the attractiveness was inferior to that of unmated females. Moreover, male moths exhibited distinct mate-selection and mating behaviors, suggesting the production of unidentified bioactive components by the sex pheromone glands of females. Gas chromatography-electroantennographic detection and gas chromatography-mass spectrometry were used to identify two additional minor components, (13E,15Z)-octadeca-13,15-dienal (E13,Z15-18:Ald) (III) and (13E,15E)-octadeca-13,15-dienal (E13,E15-18:Ald) (IV), in the sex pheromone gland extracts from M. sieversi females. The four geometric isomers of 13,15-octadecadienal were present in a relative ratio of 100 : 13.43 : 5.27: 20.04. A wind tunnel assay and field tests demonstrated that E13,Z15-18:Ald (III) played a pivotal role in the "short-range" localization of females by male moths, and exhibited a synergistic effect with Z13,E15-18:Ald (I). In contrast, Z13,Z15-18:Ald (II) and E13,E15-18:Ald (IV) had antagonistic effects. Gas chromatographic analysis revealed that the proportion of Z13,Z15-18:Ald (II) in the sex pheromone gland extracts increased markedly after mating. Furthermore, application of exogenous Z13,Z15-18:Ald (II) to the terminal segment of unmated female moths reduced mating rates, suggesting its potential role in the mating decision-making processes of M. sieversi. By clarifying the specific functional roles of minor pheromone components, this study provides a practical approach for development of precise pheromone-based control strategies against M. sieversi.