Oviposition preference and larval performance of <i>Curculio davidi</i> (Coleoptera: Curculionidae) on cultivated and wild Chinese chestnut, <i>Castanea mollissim</i> a, varieties

The chestnut weevil, Curculio davidi Fairmaire (Coleoptera: Curculionidae), is a major pest of chestnut (Castanea mollissima) production in China, but variation in susceptibility among different chestnut varieties remains poorly understood. We assessed adult C. davidi oviposition preference and larval performance on 3 cultivated varieties (Qinli 2, Hongli, and Xinzaoli) and one wild accession of Chinese chestnut in the Qinling Mountains. We also analyzed volatile organic compounds (VOCs) using GC-MS and profiled secondary metabolites (phenolic acids) to explore potential correlations between these chemical traits of chestnut and the oviposition preference and larval performance of C. davidi. In choice tests, the number of eggs laid by C. davidi females on Hongli and Xinzaoli was significantly higher than on wild chestnut and Qinli 2. In no-choice tests, oviposition on Hongli was significantly greater than on wild chestnut, Xinzaoli, and Qinli 2. Larval performance tests further showed that larval weight on Hongli was significantly higher than on wild chestnut and Qinli 2. VOC profiling identified 20 compounds, of which 13 differed significantly among varieties. Principal component analysis (PCA) of VOCs revealed that Qinli 2 formed a distinct cluster, explaining 63.5% of the total variance along PC1 and PC2. These findings suggest that host plant chemical traits influence C. davidi oviposition and larval performance, and highlight Qinli 2 and wild chestnut as potential sources of resistance for breeding programs.