To date, PWD control has focused mainly on elimination of pine
sawyer larvae inhabiting wilt pine trees, either by winter fumigation
or by controlling the adult sawyers with aerial insecticide
spray in summer. However, conventional control (C) has certain
flaws. First, approximately 18–61% of PWD wilt trees have no wilt
symptoms until the growing season in following year, and these
trees are left untreated during the winter control season (Kishi,
1995). Secondly, even branches as small as 2 cm in diameter contain
pine sawyers (Yoshimura et al., 1999) and require treatment.
Small branches are often overlooked because it is a time-consuming
task to collect them for fumigation from the scatter around felled
logs. Furthermore, transportation of fumigated logs or wilt trees for
lumber has been a main vector of long-distance spread of PWD in
Korea, accounting for approximately 38% of the PWD invasion (Shin
and Han, 2006). For these reasons, despite intensive control efforts,
PWD wilt trees appear in the same pine stands every year or occur
at new sites distant from previously infected stands. Therefore, it is
likely that preventative clear-cutting of wilt trees, including adjacent
asymptomatic pines and healthy pines followed by physical
elimination of felled logs and branches by burning or chipping (for example) will significantly suppress the reoccurrence of PWD wilt
trees within pine stands