Loop-mediated isothermal amplification (LAMP) is a technique that uses a DNA polymerase which requires only a single temperature incubation and a set of four specially designed primers that recognize a total of six distinct sequences on the target DNA for nucleic acid amplification. Due to its simplicity and robustness, LAMP has the potential to be used under field conditions, which is particular useful for surveillance, plant quarantine and infectious disease diagnosis. We report the first use of LAMP assay in Australia for the successful on-site detection of Potato spindle tuber viroid (PSTVd), a high priority emergency plant pest, in tomatoes. The LAMP assay was easy to use and the positive detection of PSTVd (from sampling to test result) was obtained in less than 40 minutes. It is envisaged that the LAMP assay validated in this study can be used by quarantine and surveillance officers for fast on-site detection of PSTVd in the near future.