New insights into the life history of Monochamus saltuarius (Cerambycidae: Coleoptera) can enhance surveillance strategies for pine wilt disease

Pine wilt disease was first discovered in Dongtang town, Liaoning Province, China, in 2017. Monochamus saltuarius Gebler is a new vector of pinewood nematode and the only known vector in Liaoning Province. The biology of this pest has not been reported thus far; therefore, it is necessary to study its life history. During 2018 and 2019, we collected 138 and 491 adult M. saltuarius beetles, respectively, to analyze their eclosion from larva to adult stage. In mid-March, overwintering larvae began to feed (on xylem) and seek nutrition in preparation for pupation and eclosion. The adults began to appear in mid-April, and the population reached its peak in late May. The life span of the adults was 28-76 days. After approximately 1 week of supplemental nutrition (feeding on twigs), adults began to mate and lay eggs. The egg stage of M. saltuarius lasted 4-8 days. The larvae in Dongtang town have 4 instars and overwinter in tunnels as 3rd-4th instars. The 1st-instar stage lasted 3-9 days, the 2nd-instar stage lasted 11-23 days, the 3rd-instar stage lasted 30-130 days, and the 4th-instar stage lasted 44-180 days. The pupal stage lasted 7-12 days, and the life span of the adults was 28-76 days. In this study we systematically monitored the life history of M. saltuarius for the first time. Our objective was to lay a foundation for improving control of this pinewood nematode vector.