Monday, November 13, 2006 - 10:15 AM

Evaluation of NTEP Bermudagrass Trial Entries for Spring Dead Spot Resistance.

Dennis Martin1, Nathan Walker2, Charles Taliaferro1, Greg Bell1, Henry Wetzel III3, and Ned Tisserat4. (1) Oklahoma State Univ., 360 Agric. Hall, Stillwater, OK 74078-6027, United States of America, (2) Oklahoma State University, 112A NRC, Stillwater, OK 74078, (3) Jacklin-Simplot, 5300 W. Riverbend Avenue, Post Falls, ID 83854, (4) Colorado State University, Bioag Sciences & Pest Management, C129 Plant Sciences, Fort Collins, CO 80523

Spring dead spot is a serious disease of intensively managed bermudagrasses (Cynodon species) and buffalograss (Buchloe dactyloides) in areas where these species experience winter dormancy. Forty-two official bermudagrass entries in the 2002-2006 National Turfgrass Evaluation Program (NTEP) bermudagrass trial and seven local standard bermudagrasses were evaluated for resistance to spring dead spot caused by the fungus Ophiosphaerella herpotricha isolate KS 188 (= isolate OK 188). Bermudagrass turf was inoculated in the field with laboratory infected wheat grain in September of 2002. Disease symptoms developed in the form of necrotic circular patches and patch diameters were measured in May of 2004, 2005 and 2006. Disease area was calculated using the formula for the area of a circle. Significant year x cultivar effects were found. ‘Ashmore’ African bermudagrass (C. transvaalensis) as well as ‘Midiron’, ‘Midlawn’, ‘OKC 70-18’, and ‘TifSport’ hybrid bermudagrasses (C. dactylon X C. transvaalensis) consistently had lower amounts of damage from the disease. ‘NuMex Sahara’, ‘Princess 77’ and Arizona common bermudagrasses (C. dactylon) often showed greater amounts of disease damage. Many other findings consistent with those gathered from the 1997 – 2001 trial were found. Information from this field screening will be useful in recommending bermudagrass cultivars with improved resistance to spring dead spot caused by this particular pathogen.