Inexpensive screening method to validate the efficacy of ethanedinitrile fumigant on the forest invasive nematode pest Bursaphelenchus xylophilus

Abstract

At a global scale, the sustainability of forests is endangered by multiple invasive species, including the pine wood nematode (Bursaphelenchus xylophilus), a quarantine pest. International laws and standards require that all exported wood coming from countries in which B. xylophilus is present be chemically or physically treated. Since a major fumigant, methyl bromide, was banned, there has been a need to generate data for alternative fumigants, such as ethanedinitrile (EDN), for this purpose. Since the field screening of fumigants (i.e., the application of various doses to and exposure times of naturally infested wood logs) is prohibitively expensive, the aim of this study was to develop a quick and inexpensive laboratory method. Here, we suggest and describe an innovative method based on sawdust cultures for EDN efficacy screening. In the validation part of this study, we demonstrated (i) the high survival of the nematodes in the sawdust and (ii) the high efficacy of EDN against this pest under in vitro conditions; 100% mortality was observed after 6 h of EDN exposure to a dose of 25 g/m3. In particular, our newly developed model system could be used for the initial screening of various doses of and exposure protocols for EDN and similar types of fumigants developed with the intention of regulating B. xylophilus occurrence in exported wood. It is believed that the validated method may help to develop new and effective EDN fumigation procedures and thereby contribute to the long-term protection of forests worldwide.