Age-Driven Olfactory Plasticity Regulates Oviposition Behavior in Mated Grapholita molesta Females in Response to Pear Fruit Volatiles

Grapholita molesta is a major fruit tree pest. Host plant volatiles act as chemical cues to mediate female oviposition. This study investigated the recognition of ovipositing G. molesta females for pear volatile blends based on age-dependent olfactory plasticity. Results showed that mated females exhibited a distinct reproduction–flight coordination window optimized at 2 days of age. Olfactory gene expression in female antennae depended on the postmating age. Nine odorant receptor (OR) genes were upregulated at 3 vs. 9 days postmating (DPM), with stronger antennal responses to trace-level odorants. RNA interference targeting ORs, especially GmolOR46, reduced antennal responses and oviposition preference at 3 DPM. Mature pears emitted more volatiles than apples, especially after mechanical injury. Females at 3 DPM were attracted to volatiles from intact or injured mature pears, particularly at high concentrations. They increased field moth catches. Our findings reveal that pear volatiles have potential as attractants for G. molesta.