Pythium soft rot (PSR) of ginger is of a major constraint for ginger production in Australia and worldwide. In Australia, the PSR outbreaks first recorded on the two oldest ginger farms in 2007 were attributed to Pythium myriotylum and since then the disease has been observed on many other farms. This study was to: (1) identify if PSR of ginger associated with species rather than P. myriotylum; (2) assess an influence of species interactions on PSR disease severity of ginger; (3) develop an accurate and rapid detection method for the associated pathogens. A total of 173 Pythium isolates belonged to 11 different Pythium species and 15 Pythiogeton (Py.) ramosum isolates were recovered from PSR ginger and soil from around infected ginger. Of these species, only P. graminicola, P. myriotylum, P. spinosum, putative P. zingiberis and Py. ramosum were isolated directly from the PSR ginger. Koch’s postulates were fulfilled with P. myriotylum, putative P. zingiberis and Py. ramosum. This is for the first time that Py. ramosum was recorded in Australia and as a pathogen on ginger. Comprehensive analyses of morphology, physiology, phylogeny and pathogenicity were allowed us to confirm species conspecificity of P. myriotylum and P. zingiberis, and P. myriotylum was the main pathogen of PSR of ginger in Australia. Co-inoculation of P. oligandrum, a well-known antagonist and P. myriotylum did not reduce PSR disease severity of ginger in pot trials. A PCR-RFLP of the CoxII fragment was successfully developed to detect P. myriotylum directly from PSR ginger sampled from pot trials.