The best way is to use the DNA barcode markers developed and validated by QBOL -Quarantine Barcode of life, The Netherlands. They have suggested suitable protocol and markers for identification of nematodes of quarantine importance. That approach will be more useful instead of trying many methods.

You can use some standard method of isolating the nematodes from sample and identify the same fist using morphlogical keys for Enoplida (Smol and Coomans 2006) and with the help of the database NEMYS (http://nemys.ugent.be/). Morphological vouchers for the specimens (digital microphotographs) are available on-line at the Nematode Tree of Life (NemATOL) web site (http://nematol.unh.edu/). Hope this will help you