We have seen Pythium sp. in turfgrass areas in the PNW in limited amounts for over 20 years. The summer of 2009 was the first time we have seen a significant amount of Pythium Root Rot on golf courses. When the temperatures hit 103 F, more irrigation was applied to the mostly Poa annua greens and the warmer temperatures combined with the moisture levels, allowed a significant amount of infection from Pythium to devastate at least 6 golf courses and cause significant damage at 4 others that we are aware of. After the initial outbreak, there was another series of samples submitted with more Pythium 6 to 8 weeks later, around Labor Day. At this time there was a spike of temperatures up to about 85 to 90 F.

When temperatures began to cool off, in mid-October, there was another outbreak of Pythium at the golf courses that were previously affected by Pythium in July. Finally, in December, there was another round of infection from cool season Pythium with the onset of winter rains and cooler temperatures on some of the same golf courses. Many of the areas that were affected were in the shady areas where the grass is in a weaker condition.

Right after this series of Pythium infections, we received a large temperature drop to freezing without any moisture and high wind speeds, which set golf courses up for dessication injury and damage to the Poa annua on greens and tees. There are reports of weakened areas from Pythium earlier in the season being severely damaged with some areas needing to be overseeded to fill in the damaged areas. We will probably see more damage show up over the next few weeks. Please let us know if this occurs so we can document the damage and try to prevent this in the future.