Preemergent Control of Medusahead on California Annual Rangelands With Aminopyralid |
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| Authors: | Guy B Kyser Vanelle F Peterson Josh S Davy Joseph M DiTomaso |
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| Institution: | 1. Specialist, Department of Plant Sciences, University of California, Davis, CA 95616, USA;2. Senior Scientist, Dow AgroSciences LLC, Mulino, OR 97402, USA;3. Cooperative Extension Farm Advisor, Tehama, Glenn, and Colusa Counties, Red Bluff, CA 96080, USA;4. Cooperative Extension Specialist, Department of Plant Sciences, University of California, Davis, CA 95616, USA;1. Graduate Research Assistant, Bioagricultural Sciences and Pest Management Department, Colorado State University, Fort Collins, CO 80523, USA;2. Research Associate, Bioagricultural Sciences and Pest Management Department, Colorado State University, Fort Collins, CO 80523, USA;3. Professor and Extension Specialist, Bioagricultural Sciences and Pest Management Department, Colorado State University, Fort Collins, CO 80523, USA;2. Associate Professor, Oregon State University, Eastern Oregon Agricultural Research Center, Burns, OR 97720, USA;3. Research Associate, Oregon State University, Eastern Oregon Agricultural Research Center, Burns, OR 97720, USA;1. Department of Natural Resources and Society, University of Idaho, Moscow, ID 83844-1139, USA;2. Department of Animal and Rangeland Sciences, Oregon State University, Corvallis, OR 97331, USA |
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| Abstract: | Medusahead (Taeniatherum caput-medusae [L.] Nevski), the most problematic invasive grass on many California rangelands, is difficult to control selectively in grasslands. Prescribed burning, grazing, and herbicides have been tested with some success but are not practical in all situations. The selective herbicide aminopyralid, normally used for control of certain broadleaf species such as thistles, suppresses some annual grasses when applied pre- or early postemergence. In 2009–2010, we tested the efficacy of aminopyralid for medusahead control in preemergence applications at three foothill rangeland sites in northern California. We compared a rate series of aminopyralid (53, 88, 123, and 245 g · ha-1 acid equivalent [ae]) with rimsulfuron (18 and 35 g · ha-1 active ingredient) and imazapic (140 g · ha-1 ae). Plots were 3 × 9 m with four replications at each site. Treatments were applied in early fall 2009. In May 2010, we took visual cover estimates and biomass/seedhead samples in three quadrats per plot. In regression analysis, medusahead cover was found to decrease consistently with increasing rates of aminopyralid. Medusahead control at the highest rates of aminopyralid was consistent across the three sites, averaging 89% ± 3 standard deviation (SD) with 245 g · ha-1 ae and 59% ± 10 SD with 123 g · ha-1 ae. Aminopyralid at lower rates, rimsulfuron, and imazapic were less consistent. Cover of other annual grasses increased in plots treated with aminopyralid at all sites. Aminopyralid has potential utility for suppressing medusahead, particularly in sites also infested with invasive members of the Asteraceae. However, the most effective rate (245 g · ha-1 ae) is registered for use only as a spot application. In situations where this rate can be justifiably used, it would be expected to give season-long control of medusahead, as well as longer-term control of thistles and other susceptible species. |
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