nematodes under surveillance

Climatic conditions in the Netherlands are similar to those of the area of pine wood nematode (PWN) distribution in North America. Environmental conditions in North America are generally unsuitable for pine wilt expression (Evans et al. 1996). According to this study, below the summer isotherm of 20 degrees expression of pine wilt disease (PWD) is not expected. It is, therefore, presumed that infested trees in the Netherlands will not express symptoms. The absence of symptoms makes it difficult to design a survey on basis of early detection without analysing a large number of samples. We explored experiences and investigations of other European countries without conditions for PWD expression (Magnusson et al, 2007; Magnusson, 2009; Schröder et al, 2009), to clarify the possibilities for a survey strategy in the Netherlands. Since the Netherlands are a major importer and exporter of products, the establishment potential of PWN (Bursaphelenchus xylophilus) is foremost determined by the possible introduction of infested longhorn beetles Monochamus in wood or wood packaging material (WPM). Therefore, the Netherlands opted for a similar strategy as other European countries where PWD symptomes are not to be expected. The monitoring o