Season-dependent synergism between the male-attractive plant volatile benzaldehyde and the sex pheromone of the Oriental fruit moth, Grapholita molesta

Herbivorous insects possess highly developed olfactory systems that enable them to detect, process, and respond to volatile cues emitted by host and nonhost plants. This study evaluated the field response of male and female Oriental fruit moths, Grapholita molesta (Lepidoptera: Tortricidae), to the aromatic plant volatile benzaldehyde (BEN). We evaluated BEN alone, in combination with the G. molesta sex pheromone, or with a four-component kairomonal lure (PHEROCON MEGALURE CM 4 K DUAL). Our findings demonstrate that (1) BEN alone is a male G. molesta attractant with efficacy comparable to that of Megalure or the sex pheromone; (2) the addition of BEN at low or medium doses to either Megalure or pheromone lures significantly increases the number of male captures; and (3) BEN interacts with the G. molesta pheromone in a season-dependent manner, exhibiting synergistic effects during the middle-season and additive effects in the early and late seasons. This discovery of seasonal synergism underscores benzaldehyde's unique role and highlights its potential to enhance pheromone-based lures without the need for additional host volatiles, providing a valuable tool for optimizing semiochemical-based monitoring and control strategies tailored to seasonal population dynamics.