Infestation of pine seedlings (Pinus thunbergii Parl.) with pine wood nematode, Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae) through needle leaves

In order to determine whether the pine wood nematode (PWN), Bursaphelenchus xylophilus can be transmitted into the pine twigs through the needles, and to identify the transmission characteristics, inoculation experiments were conducted on intact pine seedlings and detached pine needles. The experimental results indicate that PWNs could infest pine needles through wounds. Resin ducts distributed in the pine needles were the route for PWN movement. The fastest movement speed of PWN through pine needles was 2.0 cm/h, with an average fastest speed of 0.92 cm/h. PWNs could be transmitted into pine twigs within 12 h of being inoculated onto attached pine needles, ultimately leading to fatal pine wilt disease. This is the first report of PWN infestation and the induction of pine wilt disease through pine needles. After PWN infected pine needles, not all of them entered the twigs, with some nematodes colonized in the needles, where they reproduced.