Pine wood nematode (Bursaphelenchus xylophilus), the pathogen of pine wilt disease (PWD), is transmitted to new host trees through Monochamus spp., vector insects. In Korea, aerial application has been allowed conventionally to eliminate the vectors in their flying season. In this study, thiacloprid was applied to four-year-old Pinus densiflora, which were fed to adult M. alternatus emerged from PWD infected logs for 72 h in the condition of 1 DAT (Days after treatment of thiacloprid) and 15 DAT, respectively. We confirmed the presence of nematodes in each beetle applied to experiment by Baermann funnel method and PCR with species-specific ITS primers. After 72 h of 1 DAT and 15 DAT, thiacloprid residues in pine trees were 0.59-16.32 and 0.043-0.131 mg/kg and the mortalities of the beetle were 100 and 99.2%, respectively. Detection rate of B. xylophilus was 51.3%. The incidence rate of PWD in 1 DAT and 15 DAT showed no mortality and 5.55% compared with 55.5% of control, respectively.