Determination of chemotaxis response of Bactrocera dorsalis to 10 kinds of characteristic fruits in Guangxi

【Objective】Bactrocera dorsalis (Hendel) is a globally recognized destructive fruit pest that poses a significant threat to subtropical horticulture, particularly in Guangxi Province of China, where its extensive host range includes10 major local fruit species. The study utilized the following ten fruit species: Psidium guajava (guava); Citrus reticulata (Satsuma mandarin); Carica papaya (papaya); Citrus sinensis (sweet orange); Musa balbisiana (banana); Prunus salicina (Japanese plum); Hylocereus undulatus (dragon fruit); Mangifera indica (mango); Averrhoa carambola (star fruit); and Diospyros ka-ki (persimmon). This study aimed to systematically decode the chemotactic mechanisms underlying B. dorsalis host selection behavior by evaluating volatile-mediated responses to fruits under three physiological states—healthy intact, mechanically damaged, and insect-injured. The research endeavored to establish a theoretical framework for developing innovative integrated pest management (IPM) strategies by identifying key chemo attractants and behavioral thresholds, with a specific focus on optimizing sex pheromone-host volatile synergies for targeted adult control.【Methods】A Y-tube olfactometer system (glass Y-tube: arm length 10 cm, main tube length 22 cm, inner diameter 2.9 cm, 75° angle) was employed to assess behavioral preferences of B. dorsalis adults. The olfactometer was connected to odor source bottles via silicone tubing, with air pre-filtered through activated carbon and distilled water humidifiers at a flow rate of 80 mL·min-1 . Experiments were conducted under controlled conditions: 26± 1 ℃, 65%±5% relative humidity, and a 14∶10 light-dark cycle. Each treatment consisted of 20 adults per replicate, with 10 biological replicates. Test insects were introduced into the olfactometer's main tube, and choices were recorded within 15 minutes. A blank control (odorless air) was used for baseline comparison. After each test, the olfactometer was cleaned with 95% ethanol, ultrasonicated for 10 minutes, and oven-dried at 60 ℃ to eliminate residual odors. Positional bias was minimized by rotating the olfactometer 180° between replicates.【Results】All fruit volatiles exhibited significant attractant activity, but efficacy varied profoundly with species. Prunus salicina (plum) showed the highest overall attraction, with unmated males demonstrating a selection rate of 24.5%±4.0% toward healthy intact plum volatiles, while mated females reached 31.5%±4.8% for mechanically damaged plums. In contrast, Diospyros kaki (persimmon) and Averrhoa carambola (star fruit) showed the lowest responses (＜8% for most treatments), likely due to their reduced volatile organic compound (VOC) diversity. 1) Gender disparity: Females consistently exhibited stronger responses than males across all fruits (female average: 29.28%± 2.37%; male average: 25.02%±3.00%, P=0.027). This disparity was most pronounced in mated individuals, where females selected damaged fruits at a rate 19.1% higher than males, reflecting their reproductive- driven need to locate optimal oviposition sites. 2) The influence of fruit status on attractiveness: The mechanically damaged fruits induced the strongest attraction (overall average: 14.89% ± 0.98% ), with females showing peak selectivity (16.15%±1.32% for papaya and 19.0%±4.3% for plum). The GCMS analysis (supplementary data) revealed that mechanical damage increased emissions of C6 aldehydes [e.g., hexanal, (E)- 2- hexenal] and terpenoids (e.g., α- pinene), which are known herbivore- induced plant volatiles (HIPVs) that act as emergency signals for insect pests. The insect-injured fruits ranked second (13.17%±1.09%), with mango showing the highest response (27%±2.3% for mated females). The attraction to insect-injured fruits might be attributed to a combination of HIPVs and larval semiochemicals, such as oviposition-induced compounds that would be signal suitable larval development sites. The healthy intact fruits showed the lowest attraction (12.69%±1.14%), indicating that physical or biological damage significantly enhanced VOC bioactivity. 3) The influence of mating status on tropism responses to different fruits: The mated adults exhibited a 37.6% higher selection rate (15.72%± 0.92%) than unmated individuals (11.42%±0.74%), with mated females demonstrating the strongest preference for the damaged fruits. For example, the mated females selected mechanically damaged dragon fruit at 37.5%±2.3%, while the unmated females showed only 9.0%±2.2%. This suggests that mating would trigger physiological changes, such as upregulation of olfactory receptor genes, which would enhance sensitivity to oviposition-related chemical signals. A two-way ANOVA revealed significant interactions between mating status and fruit damage (F=8.72, P＜0.001). The mated females showed the highest response to mechanically damaged plums (31.5%±4.8%), while the unmated males had the low-est response to insect-injured persimmons (3.0%±2.2% ). This plasticity highlighted the importance of considering both reproductive state and fruit condition in pest management.【Conclusion】These results suggest that fruit treatment methods and varietal differences would influence the release of distinct chemo-sensory compounds, thereby modulating host selection behavior in B. dorsalis. The host-insect interaction profile established in this study could provide a theoretical foundation for developing novel control strategies, particularly in optimizing sex pheromone- host volatile synergies for targeted adult trapping and oviposition disruption. The Y-olfactometer system proved robust for quantifying behavioral thresholds, offering a reproducible method for ecological studies on insect-plant interactions. In addition, these results showed that B. dorsalis host selection was dynamically modulated by fruit physiological state, species- specific VOC profiles, and insect reproductive status. The mechanically damaged fruits emerged as the most potent attractants, likely due to enhanced emission of HIPVs that would mimic natural injury signals. The gender- and mating status-dependent responses highlighted the critical role of reproductive physiology in chemotactic behavior, with the mated females serving as the primary target for oviposition-related cues. These findings would provide a robust foundation for developing nextgeneration IPM strategies in Guangxi’s fruit orchards. Specifically, the identification of plum and mango as highly attractive hosts, combined with damage-induced VOCs, would offer opportunities to: 1) Design synthetic attractant blends that would mimic mechanically damaged fruit volatiles for enhanced trap efficiency. 2) Develop precision pest management tools by integrating sex pheromones (e.g., methyl eugenol) with host-derived attractants to target both sexes. 3) Implement cultural practices, such as post-harvest damage reduction, to minimize pest attraction in orchards.