Electrophysiological identification of 4 macrocyclic lactones as female-specific volatiles of the agarwood tree defoliator Heortia vitessoides (Lepidoptera: Crambidae).

Agarwood trees (Aquilaria spp.) are widely cultivated in tropical Asia for their valuable resin. The defoliator moth Heortia vitessoides Moore (Lepidoptera: Crambidae) is a devastating pest that significantly limits the productivity of agarwood plantations. Sex pheromones offer a sustainable and efficient approach for monitoring and controlling this pest. In this study, we report the identification of female-specific volatiles (FVs) as candidate sex pheromones produced by the female of H. vitessoides. The FVs were identified and extracted from the 3rd to 5th abdominal segments of the calling females. We combined gas chromatography coupled with mass spectrometry (GC-MS) and GC coupled with electroantennographic detection (GC-EAD) to analyze the components of the FVs in H. vitessoides. Four EAD active compounds were specific to the female abdomen, with 2 being the major components. By comparing retention times and mass spectra with synthetic racemic standards, the primary components were determined to be 4 macrocyclic lactones: 14-methyloxacyclotetradecan-2-one (A), oxacyclopentadecan-2-one (B), 16-methyloxacyclohexadecan-2-one (C), and oxacycloheptadecan-2-one (D). Further analysis using chiral standards revealed that compounds A and C possess the S configuration. GC-EAD tests on a chiral column demonstrated that all enantiomers of A and C elicited antennal responses in males, with stronger responses to the naturally occurring S enantiomers. In the choice wind tunnel assay, synthetic compounds tested individually or in blend attracted or repelled males as calling females. This study represents the first identification of macrocyclic lactones as sex pheromone candidate FVs in Lepidoptera.