Morphology of Bursaphelenchus xylophilus compared with other Bursaphelenchus species

The genus Bursaphelenchus contains about 55 species, approximately three quarters of them living in conifer trees throughout the Northern Hemisphere. The member states of the European Union have begun a survey of forest nematodes in order to try to ensure early detection of any further establishment of the pine wood nematode in Europe. Other Bursaphelenchus spp. are being, and will continue to be, found in this survey and, therefore, it is important to be able to clearly distinguish them from B. xylophilus. The Bursaphelenchus fauna of Europe shares many species with that of Asia, but is apparently clearly different from that of North America. Morphological studies of Bursaphelenchus spp. revealed that several species groups can be distinguished among the 28 species detected in Europe so far. The number of incisures in the lateral field, spicule shape, number and position of caudal papillae, presence and size of a vulval flap and the shape of female tails are essential diagnostic features. The members of the B. xylophilus group (B. xylophilus, B. mucronatus, B. fraudulentus) can easily be separated from all other species by the presence of four lateral lines, the typical shape of spicules, the special position of the caudal papillae and the large vulval flap of females. Within this group, species can be morphologically distinguished by the shape of the female tail end. The mucronate form of B. xylophilus, which is morphologically similar to B. mucronatus, does not occur in Europe. Bursaphelenchus species showing the typical features of the B. xylophilus group and having a round female tail end can, therefore, be definitely morphologically identified as B. xylophilus.