Temporal changes in pinewood nematode (PWN) populations and the percentage of third-stage dispersal juveniles (J_IIIs) of the PWN were examined on nine species of fungi growing in pine-branch segments. On Ophiostoma minus, Macrophoma sp., and Trichoderma sp. 1, the total PWN populations increased quickly for 4 weeks after nematode inoculation and then increased slightly or remained high. The number and percentage of J_IIIs also increased with time, i.e., with increasing numbers of PWNs. In contrast, the total population of PWNs decreased and the number and percentage of J_IIIs were small on Verticillium sp. and Trichoderma sp. 3.