In Northern China, the tree-of-heaven root weevil (TRW), Eucryptorrhynchus scrobiculatus (Motschulsky) (Coleoptera: Curculionidae), is a serious borer pest of Ailanthus altissima (Mill.) Swingle (Sapindales: Simaroubaceae) (tree-of-heaven) is an important tree species for landscapes and afforestation. This study evaluates the efficacy of trunk trap nets (TTN), thiacloprid spray (TS), and cypermethrin spray (CS) alone, and in combination with TTN and thiacloprid or cypermethrin spray (TTNTS or TTNCS) for controlling TRW in A. altissima plantations in 2016–2018 in three sites (Haojiaqiao, Wutongshu, and Taojiajuan), which are located near Lingwu city in Ningxia, China. TTN, TTNTS, and TTNCS treatments significantly reduce marked TRW captures (more than 93% with respect to the untreated trees) and wild TRW captures in population monitoring trunk trap nets (MTTN) deployed in stands (more than 55% with respect to the untreated trees). Further field trials demonstrate that these TTN, TTNTS, and TTNCS treatments significantly reduce damage to A. altissima in stands; there are no significant differences between TTN and combination treatments. In addition, significantly more TRW are captured in MTTN within Taojiajuan than within Haojiaqiao or Wutongshu in field trials 2018. There were no significant differences between sites in 2016 and 2017. This study indicates that the TS and CS treatments used had very little to no impact on TRW populations and tree health in the timeframe examined. TTN alone are clearly effective for suppressing populations of TRW and stabilizing A. altissima tree health. This physical control technique, using TTN, could be sufficient to manage TRW on tree-of-heaven with no insecticide.

The chestnut weevil, Curculio davidi Fairmaire (Coleoptera: Curculionidae) is a major pest of chestnuts. Damage caused by C. davidi has increased as beetle populations have expanded. To promote effective C. davidi management practices based on its host plant, we compared the susceptibility of local chestnut cultivar ‘Qinli 2’(QL2) and introduced chestnut cultivar ‘Hongli’ (HL) in Qinling Mountains to this weevil. Number of eggs laid by C. davidi females in HL was significantly higher than that of QL2. Chestnut weevil females laid 6.25-fold and 3-fold more eggs in HL than QL2 in the choice tests and no-choice tests, respectively. From 2021 to 2023, C. davidi infestation rates of HL were significantly higher than that of QL2 in the field. HL was smaller, softer, and have lower cellulose content as compared with QL2. HL contained 4.61%, 13.76%, 10.09%, 26.53%, 9.24%, 18.4%, 6.28%, and 23.26% higher amounts of N, K, Ca, Mg, S, Na, Mn, and Cu respectively, than QL2. In contrast, QL2 contained 25.28%, 19.80%, and 16.83% higher amounts of Al, B, and Fe, than HL. Our results revealed that the introduced chestnut cultivar is more susceptible to C. davidi compared to the local chestnut cultivar in Qinling Mountain, which was associated with several physico-chemical changes in chestnuts. These findings may contribute to the future efforts for breeding of C. davidi-resistant chestnut cultivars.