Monday, November 13, 2006 - 3:45 PM

Frequency of occurrence of Ophiosphaerella korrae on ‘Tifway' bermudagrass roots in Mississippi.

D. Hunter Perry, M. Tomaso-Peterson, and Gregg Munshaw. Mississippi State University, Box 9655, Mississippi State, MS 39762

Spring dead spot (SDS), caused by Ophiospharella korrae, is the most destructive disease of bermudagrass.  Spring dead spot occurs where temperatures are cold enough to induce a winter dormancy period of at least 8 w in bermudagrass in Mississippi.  The objective of this study was to monitor O. korrae occurrence in bermudagrass roots on a monthly basis throughout the year.  The study involved random sampling of bermudagrass roots within a 557 sq m area of a ‘Tifway’ bermudagrass fairway with a history of SDS.  The sampling period began in September of 2004 and will continue into 2007.  Bermudagrass root samples exhibiting discoloration associated with small, necrotic lesions were surface-disinfested and plated onto ¼ potato dextrose agar (PDA) monthly.  Light-gray, floccose mycelium characteristic of O. korrae was transferred to PDA.  Confirmation of O. korrae isolates was conducted using polymerase chain reaction (PCR).  Isolates positively identified as O. korrae were totaled for each sampling month.  Occurrence of O. korrae ranged from 1 to 17%, with the highest occurrence to date being in February of 2006.  The occurrence of O. korrae was sporadic from month to month; however, O. korrae was isolated from living roots throughout the year.  The results of this study suggest that viable O. korrae mycelium is present in bermudagrass roots throughout the year in Mississippi.