Selective control of annual bromes in perennial grass stands

Abstract

Three soil-active herbicides: atrazine [6-chloro-N-ethyl]-N1-(1-methyethyl)-1,3,5-triazine-2,4-diamine]; propham (1-methylethyl phenyl carbamate); and pronamide [3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide] were applied in the fall, postemergence to annual bromegrasses at 2 rates. These herbicides were evaluated for their efficacy in selective control of cheatgrass (Bromus tectorum L.) and Japanese brome (Bromus japonicus Thunb.) in perennial stands of crested wheatgrass (Agropyron cristatum [L.] Gaertn.), pubescent wheatgrass (Thinopyrum intermedium Host), Russian wildrye (Psathrostachys juncea [Fisch.] Nevski), and western wheatgrass (Pascopyrum smithii (Rydb.) Löve) and blue grama (Bouteloua gracilis) [H.B.K.] Lag. Ex Griffiths. Yields of annual bromegrasses and perennial grasses and crude protein (CP), phosphorus and total nonstructural carbohydrate (TNC) content of perennial grasses were measured 2 consecutive years after the single herbicide application. Yields of annual bromegrasses from the 3 herbicide treatments averaged 91 and 47% less than those of the control the first and second year posttreatment, respectively. Pronamide provided substantially better control the second year posttreatment than the other 2 herbicides. Yields of perennial grasses in the majority of the herbicide treatment-study site combinations were significantly increased the first year posttreatment (P<0.10). Crude protein of perennial grasses was increased in the atrazine treatment. Atrazine at 0.6 kg/ha was the most cost-effective herbicide for decreasing competition of annual bromegrasses and increasing yield of perennial grasses.