Plant biosecurity depends heavily on early and accurate detection and diagnosis, feeding communication chains that allow for effective mitigation. In the U.S., most land-grant university and some state/private diagnostic labs are successfully networked via the National Plant Diagnostic Network (npdn.org) and the National Clean Plant Network (NCPN), with access to training, shared protocols, and standardized communications. However, the ecosystem for plant disease diagnostic assay development, validation, and selection is siloed and detached, a critical gap in our biosecurity infrastructure, especially for new or emerging pathogens. Every assay is developed independently in a research program and then chosen independently by the end-use laboratory. This ecosystem needs to be connected, integrated, and standardized to ensure a consensus on the standards of method validation for each taxon, harmonization with our neighbors and trade partners, and availability of validated protocols and essential controls for use in emergencies as well as day-to-day detection. Extensive collaboration in the tactical sciences of plant disease diagnostic assay development and validation, reference standards, and communications platforms does not currently exist and is acutely needed. We propose development of a Diagnostic Assay Validation Network (DAVN) system to provide coordinating resources at the national level and harmonize with our partners at the international level. Here, we outline a project to stand up a DAVN with the objectives to standardize the reference standards, terminology, and statistics used in diagnostic assay development and validation via a portal of tools designed by and for the plant disease research and extension community.