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.