Regrowth of Bermudagrass Infected with Spring Dead Spot Following Low Temperature Exposure

Spring dead spot (SDS) ( Gaeumannomyces graminis (Sate.) Arx & Olivier var. graminis ) is a serious disease of intensively managed bermudagrass ( Cynodon spp.) turf throughout much of the world. Research was undertaken in North Carolina to determine (i) if exposure of previously G. graminis infected turf to low temperatures would result in the reduced bermudagrass regrowth; and (ii) if shoot regrowth potential differed between healthy and G. graminis infected bermudagrass. Bermudagrass samples extracted October through April from healthy and previously afflicted SDS areas were exposed to temperatures of −3 or −5 °C in an artificial chamber. Samples were then allowed to regrow in the greenhouse for 30 d under light followed by 20 d under dark conditions in the greenhouse. Shoot regrowth following each time period was collected, dried, and weighed. The G. graminis infected bermodagrass had 48 to 68% less shoot regrowth during winter and spring sampling periods, respectively, compared with uninfected plugs. Compared with healthy bermudagrass, G. graminis infected turf also had regrowth reduction of 41 to 71% following exposure to −3 °C after January. Reduction of shoot regrowth for G. graminis infected compared with healthy turf was as great as 95% following exposure to −5 °C. For infected turf, exposure to ‐5 °C reduced regrowth 64% more than exposure to −3 °C. Turf carbohydrate reserves, measured as shoot regrowth under dark conditions, were 70% less for infected turf compared with healthy areas during fall and winter months. In conclnsion, turf injury to G. graminis infected bermudagrass increased as low‐temperature stress increased. Injury to G. graminis infected bermudagrass occurred following low‐temperature exposure. Injury in the field occurs most often after December, but can be induced earlier by earlier exposure to −5 °C for ≥1 h.