Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 19, 2007
Publication Date: July 1, 2007
Citation: Sheley, R.L. 2007. Revegetating russian knapweed (acroptilon repens)and rabbitbrush (ericameria teretifolia)infested rangeland in a single entry. Weed Science 55:365-370. Interpretive Summary: It is critical to promote as many different species in the plant community as possible to maintain ecosystem integrity and the ability to resist invasion. Russian knapweed displaces nearly all other species. We tested the efficacy of various herbicides on controlling Russian knapweed and recovering important species, including several native plants. Glyphosate increased the richness and diversity of nonnative species, but not native species. Glyphosate may be appropriate for enhancing ecosystem function, but restoring the system with native species is unlikely using this herbicide alone.
Technical Abstract: The objective of this study was to test the potential for using a single-entry procedure to revegetate Russian knapweed– and green rabbitbrush–infested rangeland. I hypothesized that simultaneously applying an herbicide and seeding in the fall would produce the highest establishment and growth of desired species. For Russian knapweed, treatments included three seeding rates (zero, low, and high) and two herbicides (with and without clopyralid plus 2,4-D) applied in either the spring (2003) or fall (2004). The seed mixture included pubescent wheatgrass, Siberian wheatgrass, and alfalfa. Grasses were seeded on October 21, 2003 (fall dormant), and April 5, 2004 (spring), using a no-till rangeland drill. The seeding rates consisted of 3.4, 6.8, and 9.3 (low) or 5.0, 9.0, and 12.3 (high) kg ha21 of alfalfa, Siberian wheatgrass, and pubescent wheatgrass, respectively. For green rabbitbrush, treatments included two seeding levels (13.5 kg ha21 of Siberian wheatgrass and not seeded) and three herbicides (clopyralid, dicamba, and 2,4-D) and a control applied in July. Clopyralid plus 2,4-D (0.21 plus 1.12 kg ha21) and dicamba at 2.1 kg ha21 gave 61 and 66% control of Russian knapweed and green rabbitbrush, respectively. Herbicides interacted with seeding to provide the highest density of seeded species on the Russian knapweed site. These data support the hypothesis that simultaneously applying an herbicide and seeding in the fall would produce the highest establishment and growth of desired species. Conversely, only seeding affected Siberian wheatgrass establishment on the rabbitbrush sites. It may be reasonable to seed Siberian wheatgrass without controlling rabbitbrush if forage production is the primary objective.