Trunk injection of fluopyram and chlorfenapyr for efficient and long-lasting control of pine wilt disease

Chemical control is an important strategy for managing pine wilt disease (PWD). However, traditional trunk injection agents (TIAs) are constrained by limited variety and insufficient persistence. In addition, although some novel nematicides show strong activity, their large-scale forest use is restricted by high costs. Therefore, the development of cost-effective, highly efficient, and synergistic nematicidal formulations is urgently needed to advance sustainable PWD management.

This study compared the performance of combination TIAs with single-agent TIAs and a traditional TIA in terms of nematicidal activity, xylem translocation, residue dynamics, efficacy duration, and tree safety in Pinus massoniana. All six TIA formulations exhibited nematicidal activity, with fluopyram_chlorfenapyr-37 (FLU_CHL-37) TIA markedly suppressing nematode reproduction in detached branch experiments. Field trials demonstrated that all TIAs spread throughout P. massoniana within 3 months; by 18 months, residual concentrations of CHL-46, CHL-49, FLU_CHL-35, and FLU_CHL-37 were significantly higher than those of FLU-11, FLU-19, and a 20% emamectin benzoate soluble liquid (EB SL) positive control in branches 3 m above the injection site and in apical branches. Notably, FLU_CHL-37 achieved 100% control efficacy at 360 days post-inoculation, outperforming the other treatments. Safety assessments showed only slight, short-term changes in chlorophyll, malondialdehyde, and soluble protein content, all normalizing within 21 days, while local damage around the injection site was significantly less pronounced than that caused by the 20% EB SL control.

These results demonstrate that FLU_CHL-37 combines high activity, prolonged efficacy, strong translocation, and robust safety, providing theoretical and practical support for the development of novel PWD control agents. © 2026 Society of Chemical Industry.