In cool areas, dead pine trees harboring
Monochamus alternatus as a vector of pine wilt disease intermingle with those without the vector insect, due to bad synchronism between the occurrence of trees weakened by the disease and the oviposition time of the adult insects. To determine which trees were to be assigned priority in the operation to control the disease, we inspected tree trunks up to a height of 10 m using a ladder to search for any signs of
M. alternatus inhabitation and discussed about the usefulness of inspecting trees in this manner. From the ladder survey, oviposition scars and/or frass of
M. alternatus were found from 65.9% of the dead
Pinus thunbergii and
P. densiflora trees investigated. In a larger proportion of the
P. thunbergii trees, inhabitation of
M. alternatus was not detectable without examining upper part with a ladder. On the other hand, a whole-tree inspection after felling of the trees found that 35.7% of the trees displaying no sign of
M. alternatus inhabitation within the range of ladder-inspection yet harboring the insect in the uppermost part or branches. Emergence of
M. alternatus adults from logs taken from those parts of the trees in the following summer were not so abundant but incidentally reached more than 10 adults per 1 m
2 of bark surface area. Consequently, trunk survey using a ladder is considered to be useful to find infestation of
M. alternatus in dead trees, although it can not detect all of the trees harboring the insects.
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