Viability of a new recombinase polymerase reaction (RPA) test developed by Agdia, Inc. for detection of Phytophthora ramorum was assessed through a ring test developed by the USDA’s Agricultural Research Service (ARS). Four diagnostic laboratories in the National Plant Diagnostic Network (NPDN) carried out this ring test, testing 17 materials using RPA in parallel with an established enzyme-linked immunosorbent assay (ELISA). The purpose of this ring test was to determine the accuracy, repeatability, and reproducibility of RPA using different instruments for testing of P. ramorum, and assess its diagnostic potential in comparison to the existing ELISA protocol. The goals of this capstone were to carry out the RPA ring test on behalf of the Cornell University Plant Disease Diagnostic Clinic (CU-PDDC) to provide ARS with feedback on this RPA protocol and the resulting data, and to develop work instructions under the accreditation standard of the NPDN’s and CU-PDDC’s quality management system for this novel RPA test.