We conducted an operational scale trial of the herbicides Sonar® (fluridone) and Rodeo® (glyphosate) to evaluate control of giant cutgrass (Zizaniopsis miliaceae) and effects on waterfowl food plants in moist-soil managed impoundments of the Altamaha Waterfowl Management Area, Darien, Georgia. Sonar and Rodeo reduced giant cutgrass frequencies both post-treatment years, although greater reduction occurred in the Rodeo-treated impoundment. Panic grass (Panicum spp.) frequency within the Rodeo- treated impoundment decreased the first year post-treatment. First-year frequency of flat sedges (Cyperus spp.) decreased in all impoundments when compared to pretreatment frequency. However, second-year frequency did not differ from pretreatment for the Sonar or Rodeo-treated impoundments. First-year smartweed (Polygonum spp.) frequency was lower in the Sonar-treated impoundment; second-year frequency was higher in the Rodeo-treated impoundment. During the second year, wild millet (Echinocloa spp.) frequency was higher in the Rodeo-treated impoundment when compared to the control. Early fall application of Rodeo appears promising for the control of giant cutgrass and the enhancement of waterfowl food plants.
