Exposure to benzaldehyde and larval feeding experiences modulate olfactory and oviposition behaviors in female Grapholita molesta (Lepidoptera: Tortricidae).

BACKGROUND Grapholita molesta is an important pest of rosaceous fruit trees. Female oviposition affects larval infestation levels in orchards. This behavior, shaped by larval feeding experiences and female olfactory responses, points to an experience-modulated semiochemical strategy based on host plant secondary metabolites. To elucidate the combined effects of non-volatile and volatile components on female oviposition, we analyzed the volatile profiles of peach, pear, and apple shoots/fruits under intact, mechanically injured, and larval damage states throughout the growing season, along with female oviposition preferences, and compared olfactory responses (electroantennogram (EAG) and wind-tunnel experiments) and oviposition bioassays with benzaldehyde (amygdalin hydrolysate) between females with two larval amygdalin-feeding experiences. RESULTS Female oviposition preference and benzaldehyde emissions, both modulated by host factors, exhibited synchronous fluctuations. In EAG and wind-tunnel experiments, females not fed amygdalin during larval stages exhibited a strong attraction to benzaldehyde at concentrations of 10 and 0.1 μg/μL; however, females from larvae fed amygdalin showed a weaker long-distance orientation but greater responses to benzaldehyde during close-range approach and landing behaviors. Females fed amygdalin during larval stages were more likely to be responsive to lower concentrations of benzaldehyde (0.01, 0.1, and 1.0 μg/μL) for oviposition. In contrast, close-range attraction and oviposition behaviors were stronger for females that developed from amygdalin-fed larvae than those that were not fed amygdalin. CONCLUSION Dietary exposure to amygdalin during the larval stages increased the olfactory responses of females to benzaldehyde. Female oviposition behavior is co-regulated by larval experience derived from amygdalin ingestion and benzaldehyde as a host semiochemical signal. © 2025 Society of Chemical Industry.