Target To explore the control effect of 2% emamectin benzoate emulsifiable concentrate (trade name: ‘Songgaofei’) on pine wilt disease,

Methods this study first compared the nematicidal activity of 2% emamectin benzoate emulsifiable concentrate and 2% emamectin benzoate microemulsion (trade name: ‘Linyuan Songyun’) through the indoor immersion method; Then, the control effect of ‘Songgaofei’ on pine wilt disease was tested through trunk injection in the greenhouses and in the forest fields; Finally, the content of emamectin benzoate (abv. EB) in pine trees at different time points was determined by high-performance liquid chromatography (HPLC).

Results The results of the indoor immersion method showed that ‘Songgaofei’ had stronger nematicidal activity, with an LC₅₀ of 41.808 mg/L, which was significantly lower than the 75.959 mg/L of ‘Linyuan Songyun’ (p<0.05). In the prevention group, ‘Songgaofei’ displayed good protection results with no pine death of nemantode after 2 years; However, in the treatment group, the earlier the treatment was conducted, the better the treatment effect was; all the pine trees did not die when injection ‘Songgaofei’ 7 days after inoculation of nemantode, while in the group injected ‘Songgaofei ‘30 days after inoculation, P. tabuliformis had a mortality rate of 20%, and P. armandii had a mortality rate of 40%, other than no death of Pinus bungeana. Field experiments in two sites showed that the control effects of ‘Songgaofei’ were significant, with the 2-year cumulative mortality rates of P. massoniana in the experimental group being 2% and 5%, much lower than the control groups mortality rates of 20% and 25%, respectively. Residue levels of ‘Songgaofei’ in different pine species changed with time, the average content (36.59 mg·kg-1) in P. armandii was the highest, and the P. tabuliformis (27.11 mg·kg-1) is the lowest. Within15 days after injection, the residue of ‘Songgaofei’ in all pine species increased. After 15 days, the residue of ‘Songgaofei’ in all parts of tree trunk gradually decreased and stabilized finally in both P. bungeana and P. tabuliformis, except the central trunk of P. armandii, which continuously increased until day 60.

Conclusion The 2% emamectin benzoate emulsifiable concentrate ‘Songgaofei’ exhibits significant nematicidal activity against pine wood nematodes, with remarkable control effects in both greenhouse and field conditions. ‘Songgaofei’ is well-transmitted and well remained within different pine species without causing noticeable phytotoxicity, indicating a potential application in practice.