Abstract
Pine wilt disease, caused by the pinewood nematode, affects Pinus densiflora, P. koraiensis Siebold and Zucc., and P. thunbergii Parl. in South Korea. It is primarily spread by vectors such as Monochamus alternatus Hope and M. saltuarius (Gebler). However, biological control research in this context remains limited in South Korea. We identified 15 parasitoids of these vectors, namely, two ectoparasitic larval parasitoids, Cyanopterus flavator (Fabricius) and Spathius verustus Chao, both in Braconidae, Hymenoptera. A field survey was conducted in Pohang from 2018 to 2020 to elucidate the ecological and biological characteristics of these parasitoids. The average parasitism rates of C. flavator were 6.3% and 1.0%, whereas those of S. verustus were 0.7% and 0.5% on M. alternatus and M. saltuarius, respectively. Both C. flavator and S. verustus appeared to prefer M. alternatus to M. saltuarius, but a statistically significant difference was observed only for C. flavator (p < 0.001). The peak season and tree height with the highest parasitism rate of C. flavator coincided with the period when M. alternatus larvae lived beneath the bark and the highest larval density of M. alternatus and M. saltuarius occurred in pine trees. These findings provide valuable information for determining the optimal release time and height for C. flavator to achieve effective biological control.