A Multi Year Summary of Turfgrass Disease Trends in California and the Western U.S.

Diseases are a common occurrence and major concern for turfgrass managers. The objective of this study was to use data collected from 2006 to 2008 at the turf disease diagnostic clinic at the University of California, Riverside to document and analyze disease trends in the state. We examined 1,223 total samples, primarily from California but included those from Nevada, Washington, Oregon, Hawaii and Idaho. Eighty four, eighty and seventy three percent of the samples were from California in 2006, 2007 and 2008, respectively. Golf course samples constituted 95% of those received. Among cool season (C3) turfgrasses, 52 % of the diagnoses were made on annual bluegrass samples followed by creeping bentgrass (24%) and perennial ryegrass (13%).  Warm season (C4) turf constituted only 7.9 of our total diagnoses with bermudagrass samples dominating these (4.9% of total). In order of frequency, algae, rapid blight, anthracnose, summer patch, brown ring (Waitea) patch, Michrodochium patch were the most prevalent annual bluegrass diseases.  Diseases most frequently observed on creeping bentgrass were algae, take-all patch, anthracnose, summer patch, Pythium and fairy ring.  Perennial ryegrass was commonly infected by Helminthisporium leaf spot, Rhizoctonia brown patch, Curvularia blight, algae and summer patch. The diseases most commonly observed on bermudagrass were spring dead spot, Helminthisporium leaf spot, bermudagrass decline, Curvularia blight and Rhizoctonia large patch. Our results reflect the current trends in disease development on turfgrass. Rapid blight and brown ring patch are recently discovered diseases that now appear to be very common in California and the western U.S.  Anthracnose appears to be another disease common on all cool season samples. The documentation of these trends shows the major diseases and hosts for turfgrass in this region and identify where future disease management research should be directed.