Random dispersal of Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae) in Pinus densiflora branches

Abstract Bursaphelenchus xylophilus is the causative agent of pine wilt disease. These nematodes disperse in the cortical and wood resin canals of host tree branches in the early stage of infection. To determine whether the dispersal can be regarded as diffusion, we inoculated B. xylophilus into living or boiled Pinus densiflora branch sections and investigated the spatial distribution 24 hr later. Assuming that some nematodes disperse randomly in the axial direction of branch sections and the rest remain at the inoculation site, the coefficient of diffusion ( D ) by dispersers was estimated to be 23.7–40.7 and 109.4 cm 2 /day for the living and boiled branches, respectively. The proportion of nondispersers was estimated to be 0.46–0.79 and 0.52 for the living and boiled branches, respectively. When the nematodes were inoculated at the centre of upright living branch sections, they dispersed up and down at similar D values of 7.4 and 7.9 cm 2 /day, respectively.