SHRUBBY CINQUEFOIL CONTROL CHANGES RANGE FORAGE PRODUCTION

Abstract

Picloram, tebuthiuron, hexazinone, 2,4-D (isooctyl-ester), 2,4-D plus dichlorprop, and clopyralid were applied to native rangeland at two southern Alberta sites with heavy infestations of shrubby cinquefoil (Potentilla fruticosa L.). Yields of shrubby cinquefoil shoots, forbs, and grasses were measured in ungrazed areas for 4 yr after herbicide application. Hexazinone (grid-balls), 2,4-D, and 2,4-D plus dichlorprop reduced shrubby cinquefoil yields to almost zero. 2,4-D and 2,4-D plus dichlorprop increased grass yield and reduced forb yield compared with the untreated plots. Hexazinone initially decreased grass yield but, after 4 yr, grass yields were higher on the treated than on the untreated plots. Hexazinone and tebuthiuron treatments killed all vegetation within a 15-cm radius of the applied grid-balls and there was little recovery of the grasses on the tebuthiuron-treated areas 4 yr later. Picloram and tebuthiuron reduced shrub yields but many live shrubs remained after treatment. Clopyralid did not reduce shrub yields. In a further experiment, 2,4-D gave good shrubby cinquefoil control and grass yield increased. When this area was grazed the percent utilization of the total vegetation was similar for herbicide-treated and untreated areas but the amount of vegetation utilized increased by about 40% when the shrubs were controlled.Key words: Potentilla fruticosa L., picloram, tebuthiuron, hexazinone, 2,4-D, dichlorprop, clopyralid