Population Density and Host Preference of the Japanese Pine Sawyer (Monochamus alternatus) in the Qinling–Daba Mountains of China

SIMPLE SUMMARY: Monochamus alternatus is not only a serious trunk-boring pest but also the most important and effective vector of the pine wood nematode. The effective control of M. alternatus can effectively limit the spread of pine wilt disease in the Qinling–Daba Mountains. However, little is known about the damage level and host preference of M. alternatus on different host plants. Here, we investigated the population density of M. alternatus overwintering larvae and revealed the host preference and oviposition selection of M. alternatus adults on Pinus tabuliformis, P. armandii, and P. massoniana. The results improve our understanding of the host preference of M. alternatus for feeding and oviposition. ABSTRACT: Monochamus alternatus is a serious trunk-boring pest and is the most important and effective vector of the pine wood nematode Bursaphelenchus xylophilus, which causes pine wilt disease. The pine wilt disease poses a serious threat to forest vegetation and ecological security in the Qinling–Daba Mountains and their surrounding areas. In order to clarify whether the population density of M. alternatus larvae is related to the host preference of M. alternatus adults, we investigated the population density of M. alternatus overwintering larvae and explored the host preference of M. alternatus adults on Pinus tabuliformis, P. armandii, and P. massoniana. The results show that the population density of M. alternatus larvae was significantly higher on P. armandii than those on P. massoniana and P. tabuliformis. The development of M. alternatus larvae was continuous according to the measurements of the head capsule width and the pronotum width. Adults of M. alternatus preferred to oviposit on P. armandii rather than on P. massoniana and P. tabuliformis. Our results indicate that the difference in the population density of M. alternatus larvae between different host plants was due to the oviposition preference of M. alternatus adults. In addition, the instars of M. alternatus larvae could not be accurately determined, because Dyar’s law is not suitable for continuously developing individuals. This study could provide theoretical basis for the comprehensive prevention and control of the pine wilt disease in this region and adjacent areas.