Controlling Labyrinthula Terrestris by Using Soil Conditioners to Manage Soil Salinity.

Increasing population and drought has caused strain on freshwater supplies. Turfgrass managers are utilizing poorer quality water sources to conserve freshwater sources. Labyrinthula terrestris is a pathogen causing the disease known as “Rapid Blight” on certain cool season grasses including perennial ryegrass (Lolium perenne).  Occurrence and severity of Rapid Blight is dependent on temperature, locale and the soil salinity.  Rapid Blight is named after the speed in which it can kill large areas of turfgrass. Although the discovery of the pathogen and disease is relatively recent, it is more frequently diagnosed in part because of the use of saline water for irrigation resulting in soil salinization.  This can be a particular problem in areas subject to drought conditions. The objective of this study was to identify if control of Rapid Blight could be obtained by managing soil salinity with the use of soil conditioners. Two, six week experiments were conducted during the fall-winters of 2008 and 2009 in a greenhouse in Florence, South Carolina, USA. Perennial ryegrass was grown in PVC lysimeters and inoculated with L. terrestris. The grass was subjected to a two-way factorial of four saline water treatments (0.1, 1.5, 3.5, and 5.0 dS m^-2) and four soil conditioner treatments (none, gypsum, and two experimental conditioners).   The influence of conditioners on leachate and soil salinity as well as visual quality and disease severity varied. Applying gypsum postponed disease the longest. Managing soil salinity by weekly use of soil conditioners applied with irrigation water reduced disease severity.