Abstract: The variations of the reproduction of cultured Bursaphelenchus xylophilus on 9 different species of fungi and the pathogenicity on 3 years old Japanese black pine (Pinus thunbergii) were studied. The reproductions of the nematodes on fungi was decreasing as the following fungal cultures of Botrytis cinerea, Pestalotiopsis sp., Pestalotia sp., Phomopsis sp., Phoma sp., Cephalosporium sp., Alternaria sp., Colletotrichum sp. and Ceratocystis sp..The nematodes cultured on these fungi were inoculated on the seedlings of P.thunbergii and pathogenicity of B.xylophilus was decreasing as the same fungal culture sequence as the nematode reproduction.The variation in the pathogenicity of the B.xylophilus was consistent with the fungi reproductivity.