Methods were developed for screening Prunus selections for host suitability to Criconemella xenoplax. The relative host suitability of selections was based upon a doubling accumulation value (beta) that was defined as the number of degree-days (base 9 C) required for doubling of an increment of the initial nematode population. The beta value characteristic for C. xenoplax (139 +/- 8 degree-days) on suitable hosts was similar to the average beta value determined for several peach rootstocks known to be suitable hosts. The beta values were 144 +/- 21 for Halford, 141 +/- 16 for Lovell, and 138 +/- 10 for Nemaguard. A higher value for beta could indicate poorer host suitability or resistance of a selection to C. xenoplax. All of 369 Prunus accessions tested, including eight accessions that had survived well on a field site infested with C. xenoplax, were suitable hosts. Apparently, resistance to C. xenoplax was not a factor in survival of the accessions planted in the field. Seedlings from P. besseyi, P. pumila 'Mando', and two interspecific hybrids, Redcoat and Sapalta IR 549-1, failed to support nematode population increase in 44-81% of tests conducted, but all selections supported population increase in some tests. These accessions may have resistance mechanisms that are active only under specific conditions.