Effects of the wet catching method on the detection of Bursaphelenchus xylophilus from trapped longhorn beetle vectors

The pine wood nematode (PWN), Bursaphelenchus xylophilus, causes pine wilt diseaseand is transmitted by Monochamusbeetles. An efficient trapping system for these organisms is essential for their early detection in threatened regions. A wet catching method, using monoethylene glycol (MEG) in a collecting cup to preserve captured insects, was suitable for catching longhorn beetles. As a second step in developing this technique, we studied the influence of MEG on nematode detection. When M. galloprovincialis carrying PWN were submerged in MEG, nematodes died within 24 h. The preservative altered certain morphological features of nematodes immersed in solutions of 10, 30 or 60% MEG, impeding their morphological identification. However, molecular identification was possible as long as the MEG concentration was below 70%. At higher concentrations, a rinsing step with water before DNA extractionwas enough to allow molecular detection. Wet trapping requires less frequent monitoring than dry trapping, thus reducing maintenance and related costs.