Several species of Pythium have long been known to be pathogenic to intensely managed stands of turfgrass.  In the Pacific Northwest, during the summer of 2009, several golf course greens were damaged by what appears to be a Pythium pathogen.  Initial damage appeared after 3 days of 32C with humid nights of 18C. Damage continued throughout the winter and through the entire season of 2010 and the spring of 2011 at lower temperatures of between 2 and 10C. Samples from 50 golf courses were received at the WSU Plant Diagnostic Clinic as a result.  Infected shoots, as well as the roots, from these samples have been isolated and cultured on a V8 growing medium. Forty isolates were sequenced and several species of Pythium have been identified by comparing their sequences with known Pythium spp. using BLAST. Results have varied between samples, with several species being identified.  Pythium vanterpoolii and P. torulosum have been detected consistently in foliar and root samples.  Once a complete collection of Pythium isolates has been gathered, they will be used to perform Koch’s postulates by re-infecting stands of Poa annua to determine whether these species of Pythium are causing damage to golf greens or if the damage is an interaction between management practices, climate, and the presence of these organisms.