Wednesday, November 15, 2006
249-2

Southern Blight on Annual Ryegrass in Texas.

Lloyd Nelson and K. C. Steddom. Texas A & M University, PO Box E, Overton, TX 75684-0290, United States of America

 

Southern Blight caused by Sclerotium rolfsii Sacc. resulted in loss of many space planted plants of Lolium multiflorum Lam. at Overton, Texas in 2005.� This disease epidemic occurred during April and May, when annual ryegrass plants were heading out.� The disease occurred on both forage-type tetraploids plants as well as dwarf turf-type diploid plants.� Nurseries went through drought conditions, followed by moist growing conditions with heavy dews.� Several days of warm weather with day time temperatures near 34 C likely contributed to the epidemic.� A few plants begin to show brown to redish leaves, followed by entire plants showing symptoms similar to drought or heat stress and then death of plant over approximately 5 days.� Over a 10 day period, approximately 80% of plants were heavily diseased in some nurseries.� Healthy plants were observed adjacent to dead plants.� When inspecting the crown and roots system, crowns were rotted and� most roots had died.� Also many white and brown sclerotia (1 to 2 mm) were observed in the crown area of the plants.� In adjacent pastures, where ryegrass was growing, the disease was not observed.� The disease was also not apparent in over seeded (annual and perennial ryegrass) turf plots.