Diagnostic assays for plant pathogens are a critical component in the surveillance, detection, and management of disease in the production of food, feed, and fiber. Producers, crop consultants, and state and federal officials depend on rapid and accurate diagnostics for response, disease mitigation, crop management, and regulatory decisions affecting trade and export prices. Diagnostic assays undergoing development must be validated to understand how well the assay will perform on given sample matrices, in different user hands, and under varying laboratory conditions before deployment and application in diagnostic clinics and distribution as commercially available assays. The validation of diagnostic assays is a time-consuming, expensive, multitiered process, requiring pathogen and near neighbor reference materials, barcode and/or genome sequence data, and cross-laboratory partnerships. Regulatory agencies and diagnostic clinics do not often have fully validated assays to deploy during an outbreak of a novel pathogen. Our survey of recent publications describing the development of diagnostics for plant pathogens found that those detailing an appropriate and robust diagnostic assay validation process were few in number. The results point out the need for broad application of standards and rigor in the conception, development, and execution of diagnostic assay validation. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .