The pine wood nematode Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle (=B. lignicolus Mamiya and Kiyohara) : An assessment of the current position

Summary Pine wood nematode, Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle, is the casual organism of pine wilt disease, a major tree killer in the Far East. This paper describes the biology of B. xylophilus, particularly its inter-relationships with vector insects in the genus Monochamus (Coleoptera: Cerambycidae), tree species and environmental conditions. The principal method of transmission, and hence of international plant health significance, is introduction of nematodes to susceptible dying or dead trees during female oviposition. This occurs in all countries where the nematode occurs but is the only significant method of transmission and survival of B. xylophilus in North America. Extensive tree mortality in Japan and China is associated with presence of highly susceptible tree species, suitable vector species and high summer temperatures. Pest risk assessments have been carried out to determine the risks to Europe; it is concluded that the nematode would undoubtedly survive in Europe but that tree mortality is likely only in the warmer southern countries. Methods to prevent transfer of nematodes to Europe are discussed in relation to European Union legislation.