Abstract/Contents: | "Roundup ProDry (RPD), Roundup Pro (RP), old formulation of Roundup (ROF), an experimental Roundup (EXR), and Roundup ProDry + Reward (R + R) were applied to tall fescue to evaluate rainfastness. Roundup formulations were applied at 6.7 kg acid equivalents/ha. No irrigation or irrigation was applied at 6.4 mm or 2.5 mm at 15, 30, or 60 minutes after herbicide applications (MAHA). At 1 week after treatment (WAT), control with RPD, RP, ROF, EXR, and R+R were 53, 58, 54, 51, and 81% respectively, for no rainfall, and 26, 31, 24, 35, and 71%, respectively, for 6.4 mm rainfall applied at 60 MAHA. No differences between 60, 30, or 15 MAHA were noted 1 WAT. At 4 WAT, control with RPD, RP, ROF, EXR, and R+R were 100, 100, 99, 99, and 90% control, respectively, for no rainfall, and 94, 97, 90, 97, and 86% control, respectively for 6.4 mm rainfall applied 60 MAHA, and 88, 88, 84, 91, and 84% control respectively for 6.4 mm rainfall 15 MAHA. Results were not different with 2.5 mm vs. 6.4 mm rainfall. These data indicate Roundup is more rainfast on tall fescue than the label suggests. Also, ROF performed similar to newer Roundup formulations. In general, rainfall decreased control more at 1 WAT than 4 WAT. R+R showed more rapid burndown at 1 WAT but antagonism at 4 WAT." |