Mari-Vaughn V. Johnson1, James R. Kiniry1, and Mark Weltz2. (1) USDA-ARS, Grassland, Soil, and Water Research Laboratory, 808 East Blackland Road, Temple, TX 76502, (2) USDA-ARS, Exotic and Invasive Weeds Research Unit, 920 Valley Road, Reno, NV 89512