Factors Affecting Both the Numbers of the Pinewood Nematode, Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae), Carried by the Japanese Pine Sawyer, Monochamus alternatus (Coleoptera: Cerambycidae), and the Nematode's Life History

The Japanese pine sawyer, Monochamus alternatus, which emerged from wood blocks inoculated with a species of blue-stain fungus Ophiostoma minus, carried a far greater number of pinewood nematodes (PWNs), Bursaphelenchus xylophilus, than those from wood blocks inoculated with Trichoderma sp. 2, Trichoderma sp. 3 or uninoculated blocks. This was because: 1) PWNs propagated much better in the O. minus-inoculated blocks than in the Trichoderma spp.-inoculated or uninoculated blocks; and 2) the ratios of third-stage dispersal juveniles and dauer juveniles to total PWNs, and the ratio of PWNs which transferred to a beetle to total PWNs were much higher in the former than in the latter. Third-stage dispersal juveniles occurred even in the absence of M. alternatus, however, the presence of M. alternatus raised their percentage. In contrast, M. alternatus was essential for the occurrence of dauer juveniles. The species of jungi dominating the dead wood might determine the number of PWNs carried by the beetles which emerge from the wood.