Russian olive is an invasive, woody species that is overtaking riparian areas and pastures in the Western United States. Studies show that diversity of avian and mammalian species decrease as Russian olive replaces native vegetation. Its thorns discourage livestock grazing and are hazardous to humans and farm equipment. The label of one glyphosate product states, “For best results, [cut stump] applications should be made during periods of active growth and full leaf expansion.” The major concern with the growing season application is that farmers and ranchers are busiest during that time of year, so Russian olive control is moved toward the bottom of the list of things to do. This field trial in east central Utah was to determine which times of year a cut stump application of glyphosate or imazapyr would be most effective.

From December 2009 through November 2010, six Russian olive trees were cut down each month. Three stumps were immediately treated with undiluted 41% glyphosate herbicide applied to the cambium layer at the rate of 1 cc herbicide per inch of trunk diameter. Three stumps were untreated controls. From December 2010 through November 2011, nine Russian olive trees were cut down each month. Six stumps were immediately treated with two glyphosate products and three were treated with imazapyr. The results indicate that 100% dormant and growing season control can be achieved with cut stump treatments of glyphosate or imazapyr on Russian olive, thus allowing farmers and ranchers more time to schedule Russian olive control.