Further Identification of Pythium Species Causing Damage On Golf Course Greens in the Pacific Northwest.

Several species of Pythium have been described as pathogens of highly maintained turfgrass cultivars.  Historically, pathogenic activity manifested during periods of high heat and humidity.  West of the Cascade Mountains, in the Pacific Northwest - a marine climate - temperature extremes are uncommon.  Rarely do summer temperatures rise above 30 degrees Celsius, and rarely are Pythium infections a consideration.  This trend was broken in July of 2009.  Combined with warm and humid nights, temperatures hovered around 32 degrees Celsius for three consecutive days, and then finally climbed to a record-breaking 103 degrees Celsius.  Samples, from golf courses, of dead, dying, yellow, and thinning turfgrass were sent to the WSU Plant and Insect Diagnostic Clinic.  While the temperatures eventually abated, the samples did not.  Several golf course superintendents in the Puget Sound area battled Pythium throughout the fall and winter of 2009 and through 2010.  During the winters of 2009 and 2010, 58 samples were collected, and an additional 6 samples were received in the winter of 2011.  From these sample submissions, approximately 60 isolates have been cultured.  An additional growth chamber experiment is planned.  But, as a step toward that project, understanding the optimal temperatures at which these isolates grow is important.  To measure growth rates of Pythium isolates, a 5mm V8 agar plug - taken from the growing edge of the Pythium colony - will be centered in a petri dish filled with similar V8 agar media.  Colony growth measurements will be taken at 12-hour intervals, measuring radial growth at two perpendicular points on the leading edge of the hyphae.  The isolate growth will be tested at varying temperatures to assess and produce growth curves.