Effect of Picloram on Cinquefoil and Forage Production at the Ya-Ha-Tinda Ranch, Alberta

Abstract

Grass production at the Ya-Ha-Tinda Ranch, Alberta, decreased during the last two decades and shrubby cinquefoil (Potentilla fruticosa L.) and forb production increased, probably as a result of overgrazing by elk and horses. In 1970, plots on three pastures on the ranch were sprayed with 0.5, 1.0, and 1.5 lb/acre of the herbicide, picloram, to determine its effect on shrubby cinquefoil, and on forb and grass production. In 1971, 1972, and 1973, the plots were examined for percent shrub kill, and they were clipped in 1971 and 1972 to determine forb and grass production. Fifty-six to 99% of all shrubby cinquefoil plants were killed following treatment with different levels of picloram. Total forb production on all three pastures decreased, although sweet-flowered androsace (Androsace chamaejasme Host) and old man's whiskers (Geum triflorum Pursh) showed some resistance to the herbicide. Following the 1970 spraying with picloram, grass production increased by 53% in 1971 and 77% in 1972. However, grasses and sedges also increased by 34% in control plots from 1971 to 1972 because of protection from grazing and favorable precipitation.