Abstract
Two species of Bursaphelenchus nematode which were different in their pathogenicity to pine trees were inoculated onto the seedlings of Pinus thunbergii and P. densiflora, and dispersion and population density of both nematodes in the inculated seedlings were examined once a week for 8 weeks. Pathogenic B. lignicolus dispersed and propagated rapidly in all inoculated seedings of P. thunbergii but failed to disperse and propagate in some of the inoculated seedlings of P. densiflora. On the other hand, non-pathogenic B. mucronatus hardly propagated in both pines except in a few seedlings thought nematodes of this species could disperse as well as B. lignioclus. Rapid dispersion accompanied with propagation of nematodes always resulted in weakening or death of hosts irrespective of the species of pine and nematode examined, though a few dead seedlings without so many nematodes were observed 6-8 weeks after inoculation.
