This new online publication, written by regional nematologists, provides good comprehensive information about conducting strip trials to compare seed treatments and nematodes in corn.
It outlines how multiple samples must be collected uniformly, consistently, carefully, and at the proper time in order to have a chance of detecting differences in nematode population densities among treatments.
More corn nematode resources:
Quick Facts about Nematodes in Corn – Iowa State University
Ten Things You Should Know About Corn Nematodes – University of Illinois