• Annual Grass Control in Established Mohave Valley Alfalfa Using Thiazopyr (Visor), Trifluralin (Treflan) and Norflurazon (Zorial)

      Knowles, Tim C.; McCloskey, William B.; Wakimoto, Vic; Ottman, Michael J.; La Paz County Cooperative Extension, University of Arizona, Parker, AZ; Department of Plant Sciences, University of Arizona, Tucson, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1999-05)
      Annual grasses such as wild barley and Mexican sprangletop are of economic concern to alfalfa growers in western Arizona. Thus, granular formulations of thiazopyr (Visor 2.5G), trifluralin (Treflan TR-I0), and norflurazon (Zorial 5G) herbicides were evaluated for annual grass control in an established alfalfa field in Mohave County when applied after the first hay cutting in early spring and prior to irrigation. Visor 2.5G was applied in spring 1998 and 1999 at application rates of 0.25, 0.38, and 0.5 lb a.i./acre. Treflan TR-10 was applied at 2.0 lb a.i./acre in early spring or in both early spring and late summer. Visor 2EC was applied at 0.5 lb a.i./acre in spring 1998 but was replaced with Zorial 5G at 2.0 lbs a.i./acre in spring 1999. In 1998, good wild barley control (81%) resulted from a spring application of Visor 2.5G at 0.50 lb a.i./acre. The Visor 2EC formulation at 0.5 lb a.i./acre provided poor weed control (40 %) due to the retention of herbicide on the alfalfa foliage and lack of incorporation into the soil by irrigation. In 1999, fair wild barley control (73 to 79 %) resulted from spring applications of Visor 2.5G at 0.50 lb a.i./acre and Zorial 5G at 2.0 lb a.i./acre. During summer 1998, good Mexican sprangletop control (83-93 %) resulted from Visor 2.5G applied at 0.38 and 0.50 lb a.i./acre and Treflan TR-10 applied in both spring and summer at 2.0 lb a.i./acre. No alfalfa phytotoxicity was observed at the rates applied in this study.
    • The Use of Norflurazon (Zorial 5G) in Parker Valley Alfalfa for Purple Nutsedge Suppression in 1998-99

      Knowles, Tim C.; McCloskey, William B.; McGuire, Jerry; Ottman, Michael J.; La Paz County Cooperative Extension, University of Arizona, Parker, AZ; Department of Plant Sciences, University of Arizona, Tucson, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 1999-05)
      An experiment was conducted in 1998-99 to study the efficacy of spring (April 30, 1998 and March 4, 1999) applications of Zorial 5G (1, 1.5, 2, 2.5, and 3 lb a.i./A), Treflan TRIO (2 lb a.i./A), and Visor 2.SG (0.25 and 0.5 lb a.i./A) on purple nutsedge control in alfalfa. The second half of split Zorial 5G (1+1, 1.5+1.5, and 2 +1 lb a.i./A per year) and Treflan TRIO (2+2 lb a.i./A per year) treatments were made each summer (September 8 and June 22). Purple nutsedge suppression on May 27, 1998 increased linearly as the rate of Zorial 5G applied increased from 1.5 to 3 lb a.i./A. The degree of nutsedge suppression resulting from the initial spring Zorial 5G applications increased with time, reached a maximum on August 4, 1998 (52 to 72 %), and declined later in the fall. Split spring and summer applications of Zorial 5G at annual rates of 2 or 3 lb a.i./A provided good (80-88 %) purple nutsedge suppression in the fall of the first year of this study although the single spring applications of 2 or 3 lb a.i./A provided greater suppression in the spring and early summer. Similar to 1998, there was a slow increase in Zorial 5G efficacy on purple nutsedge during the spring of 1999 with the single spring 1.5 to 3 lb a.i./A Zorial 5G applications resulting in very good control (89-96 %) on June 22, 1999. The annual application rate of 1 lb a.i./A Zorial 5G resulted in only fair purple nutsedge control (at best 75 %) and was significantly worse than the other Zorial treatments. During June, July and August of 1999, there were no significant differences between treatments that received 1.5, 2, 2.5 or 3 lb a.i./A Zorial in a single spring application. In addition, there were no significant differences in purple nutsedge control between treatments that received greater than 1.5 lb a.i./A in a single spring application versus treatments that received split applications of Zorial 5G. Thus, the split 2 lb a.i./A Zorial SG treatment and the two split 3 lb a.i./A treatments were not significantly better than the single spring applications of 2 and 3 lb a.i./A, respectively, during the second year of this study. To date, single applications of Visor 2.5G at 0.25 and 0.5 lb a.i./A and the split Treflan TRIO treatment (2+2 lb a.i./A per year) have provided poor purple nutsedge suppression in 1998 (0-25 %) and 1999 (0-5 %).