Migrations and Multiplications of Bursaphelenchus xylophilus and B. mucronatus in Pinus thumbergii in Relation to Their Pathogenicity

To evaluate the mechanisms of pathogenicity and nonpathogenicity of Bursaphelenchus xylophilusand B. mucronatus isolated in South Korea, we used 4-year-old P. thunbergii seedlings and 20-cm long one-year-old stem cuttings of 5-year-old Pinus thunbergii, and studied distributions and multiplications of pine wood nematodes after inoculation. The distributions of B. xylophilusin the 20-cm pine stem cuttings were not significantly different from that of B. mucronatus. Conversely, the proliferation rate of B. xylophiluson mycelial mats of Botrytiscinerea was significantly different from that of B. mucronatus. The study using 4-year-old P. thunbergii seedlings also showed that B. mucronatus can migrate to distal portions of the pine seedlings the same as B. xylophilus, but the populations of B. xylophilusremaining in the pine seedlings were relatively larger than those of B. mucronatus. Therefore, we concluded that the pathogenicity of B. xylophiluscould be strongly influenced by its ability to multiply.