Movement of the pinewood nematode, Bursaphelenchus xylophilus, through tracheids in diseased pine trees

Abstract

The pinewood nematode (hereafter PWN), Bursaphelenchus xylophilus, is a causal agent of pine wilt disease (Kiyohara and Tokushige, 1971). So far, studies on the movement and reproduction of PWN in pine trees have been conducted with the aim of elucidating the role of PWN in the course of disease development (Mamiya, 1974,1975,1980,1985).Histological observations on diseased and dead pine trees demonstrated that PWN inhabited mostly resin canals and rays of pine trees (Mamiya and Kiyohara, 1972; Mamiya, 1975, 1980, 1985; Yik and Birchfield, 1981; Bergdahl, 1982; Myers, 1984; Kuroda and Mamiya, 1986). In the wood of pine trees, PWNs use the network of resin canals in the xylem as a passage for movement. PWN is also known to use parenchyma cells as the most likely source of food (Kuroda and Mamiya, 1986).The objective of this histological study is to use microphotographs to indicate nematode movement through tracheids of the xylem in the Japanese red pine, Pinus densiflora, and also show aggregation of PWN around the pupal chamber of the Japanese pine sawyer, Monochamus alternatus.