Submitted to: Oregon State University Extension Publications
Publication Type: Government Publication
Publication Acceptance Date: 11/20/2012
Publication Date: 11/29/2012
Citation: Johnson, D.D., Davies, K.W. 2012. Revegetating sagebrush rangelands invaded by medusahead. Oregon State University, Oregon Beef Council Report [online]. BEEF094. Available: http://beefcattle.ans.oregonstate.edu/documents/BEEF094-RevegetatingSagebruch.pdf Interpretive Summary: Medusahead infestations are often controlled with imazapic herbicide treatments because medusahead invasion decreases biodiversity, degrades wildlife habitat, and reduces livestock forage production. After medusahead control there is often a need to revegetate the plant community. However, there is disagreement if native or introduce vegetation establish better and if seeding can occur immediately after imazapic treatment or should occur one year later to limit herbicide damage to seeded vegetation. We evaluated seeding native and introduced plants and seeding timing after imazapic application (immediately and one year later) at five sites. Initial results indicated substantially greater establishment of introduced species over native plants. Preliminary results also indicated that seeding immediately following application of imazapic is not a viable restoration option because of non-target herbicide damage to the seeded vegetation.
Technical Abstract: The objectives of this study were to determine: 1) effective treatments for controlling medusahead and 2) the appropriate plant materials for revegetating medusahead-invaded rangelands. Initial treatments of prescribed burning immediately followed with applications of the preemergent herbicide imazapic (Plateau ®) were applied to three 130 x 165 ft plots at each of five sites in eastern Oregon during the fall of 2010. The same treatment combination was applied to an additional 130 x 165 ft plot at each of the five sites during the fall of 2011. All burned and herbicide treated plots were seeded during the fall of 2011 with either a mix of introduced species, native species, or a combination of introduced and native species. The study also included an untreated reference plot at each of the five sites. Prescribed burning followed with an application of imazapic at a rate of 6 oz/ac substantially reduced medusahead cover and density compared to the untreated reference plots. Fall prescribed burning to remove persistent medusahead litter followed immediately with an application of imazapic at a rate of 6 oz/ac is an effective treatment combination for controlling medusahead and preparing sites for successful revegetation of desirable plants. Initial revegetation success of seeded plants following medusahead control indicated substantially greater establishment of introduced species over native plant materials. Initial results also indicated that reseeding immediately following application of imazapic is not a viable restoration option because of non-target herbicide damage to the seeded vegetation. Instead, our preliminary results suggest initial establishment of seeded plants is best facilitated by using seed mixes predominantly comprised of introduced plant materials and waiting a year after imazapic application before revegetation efforts are attempted.