Several molecular methods have been developed for detection of Erwinia amylovora, the causal agent of fire blight in pear and apple, but none are truly applicable for on-site use in the field. We developed a fast, reliable and field applicable detection method using a novel target on the E. amylovora chromosome that we identified by applying a comparative genomics pipeline. The target coding sequences (CDS) are both uniquely specific for and all-inclusive of E. amylovora genotypes. This avoids potential false negatives that can occur with most commonly used methods based on amplification of plasmid gene targets, which can vary among strains. Loop-mediated isothermal AMPlification (LAMP) with Optigene GenieII chemistry and instrumentation proved to be an exceptionally rapid (under 15 minutes) and robust method for detecting E. amylovora in orchards, as well as simple to use in the plant diagnostic laboratory. Comparative validation results using plant samples from inoculated greenhouse trials and from natural field infections (of regional and temporal diverse origin) showed that our LAMP had equivalent or greater performance regarding sensitivity, specificity, speed and simplicity than real-time PCR (TaqMan), other LAMP assays, immunoassays and plating, demonstrating its utility for routine testing.