Participation of .BETA.-myrcene in the susceptibility and/or resistance of pine trees to the pine wood nematode, Bursaphelenchus xylophilus

The relationship of the β-myrcene content with the susceptibility and/or resistance of Pinus species against the pine wood nematode was investigated. For this purpose, the β-myrcene content of the wood of one-year-old shoots was determined. The resistant trees were found to contain a very small amount of β-myrcene. On the other hand, the β-myrcene content of susceptible trees was comparatively high. This relationship was observed in both inter- and intraspecies and also between young and older trees of the same species, i.e., Pinus densiflora or P. thunbergii. The β-myrcene content can feasibly be used as an indicator for screening resistant Japanese red and black pine trees.