The use of a herbicide as a tool to increase livestock consumption of medusahead (Taeniatherum caput-medusae)

Authors: Stonecipher, Clinton - Clint; SPACKMAN, CASEY - New Mexico State University; Panter, Kip; VILLALBA, JUAN - Utah State University

Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2021
Publication Date: 6/1/2021
Citation: Stonecipher, C.A., Spackman, C., Panter, K.E., Villalba, J.J. 2021. The use of a herbicide as a tool to increase livestock consumption of medusahead (Taeniatherum caput-medusae). Invasive Plant Science and Management. 14(2):106-114. https://doi.org/10.1017/inp.2021.12.
DOI: https://doi.org/10.1017/inp.2021.12

Interpretive Summary: Medusahead is an invasive annual grass that is altering the vegetation dynamics of rangelands in western North America. Finding inexpensive tools that can be used to remove medusahead would be beneficial to land managers. Combing the application of glyphosate to medusahead followed by targeted grazing of the treated medusahead resulted in a decrease of medusahead and its thatch layer. The removal of medusahead and its thatch layer through targeted grazing provides a seed bed for the fall planting of desirable perennial species.

Technical Abstract: Medusahead [Taeniatherum caput-medusae (L.) Nevski] is an invasive annual grass impacting rangelands throughout the western United States. Treatment of T. caput-medusae invaded rangelands with glyphosate followed by targeted grazing is a practical, economical, and efficient method to fully utilize and control the weed. Furthermore, utilizing the combination of these tools may assist in preparing the ground for fall seeding with desirable perennial species. We tested cattle (Bos taurus Linnaeus) utilization of T. caput-medusae following treatment with glyphosate in two forms of its salt (potassium salt and isopropylamine salt) at three different rates of application; low (236 g ae ha-1), medium (394 g ae ha-1), and high rate (788 g ae ha-1) in eastern Washington. The herbicide was applied on April 26, 2016. A second site, northern Utah, was treated with glyphosate in the form of its isopropylamine salt at the high rate. The herbicide was applied on June 5, 2019. Cattle were allowed to start grazing T. caput-medusae 3-weeks after glyphosate treatment and had unlimited access to the glyphosate treated plots for over 85 days. The greatest utilization of T. caput-medusae occurred at the highest glyphosate application rate (P < 0.05), in Washington, with no difference between forms of glyphosate salt. Glyphosate treatment preserved the water-soluble carbohydrate content of T. caput-medusae at levels greater than the non-treated controls (P < 0.05) at both locations. The glyphosate treatment assisted in the increased utilization of T. caput-medusae by cattle and is a viable option for the removal of T. caput-medusae while increasing the forage value of the weed.