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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #344924
Title: Timing aminopyralid to prevent seed production controls medusahead (Taeniatherum caput-medusae) and increases forage grasses

Author
item Rinella, Matthew - Matt
item DAVY, JOSH - University Of California
item KYSER, GUY - University Of California
item MASHIRI, FADZAYI - University Of California
item Bellows, Susan - Bartlett
item JAMES, JEREMY - University Of California
item PETERSEN, VANELLE - Retired Non ARS Employee

Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2017
Publication Date: 4/5/2018
Citation: Rinella, M.J., Davy, J.S., Kyser, G.B., Mashiri, F.E., Bellows, S.E., James, J.J., Petersen, V.F. 2018. Timing aminopyralid to prevent seed production controls medusahead (Taeniatherum caput-medusae) and increases forage grasses. Invasive Plant Science and Management. 11(1):61-68. https://doi.org/10.1017/inp.2017.41.
DOI: https://doi.org/10.1017/inp.2017.41

Interpretive Summary: Exotic annual grasses dominate millions of hectares of grasslands in the western U.S. Among other herbicides, growth regulators such as Milestone and Tordon have been tested against these invaders. Recent studies demonstrate growth regulators applied at late growth stages drastically reduce seed production in cheatgrass, medusahead and other annual grasses. In eight experiments in California annual grasslands, we tested if using aminopyralid to reduce medusahead seed production translates into reduced medusahead cover. We applied aminopyralid at 55, 123 and 245 g ha-1 just prior to medusahead heading in spring, and to allow comparisons to a previously tested timing, we also applied the two higher rates pre-emergence in fall. When applied at just 55 g ha-1 in spring, aminopyralid controlled seed production and consistently reduced medusahead cover to near zero. Aminopyralid applied fall was less effective, even at the 245 g ha-1 rate. Unlike spring treatments, fall treatments sometimes reduced cover of forage grasses the first growing season. At final measurement, both spring and fall treatments tended to increase forage grasses, but spring treatments sometimes caused larger increases. Compared to other herbicide options, aminopyralid applied pre-heading appears to be a relatively inexpensive, more effective way to manage medusahead in annual grasslands.

Technical Abstract: Exotic annual grasses dominate millions of hectares of grasslands in the western U.S. Among other herbicides, growth regulators such as picloram and aminopyralid have been tested against these invaders. Recent studies demonstrate growth regulators applied at late growth stages drastically reduce seed production in Bromus tectorum L., Taeniatherum caput-medusae (L.) Nevski and other annual grasses. In eight experiments in California annual grasslands, we tested if using aminopyralid to reduce T. caput-medusae seed production translates into reduced T. caput-medusae cover. We applied aminopyralid at 55, 123 and 245 g ha-1 just prior to T. caput-medusae heading in spring, and to allow comparisons to a previously tested timing, we also applied the two higher rates pre-emergence in fall. When applied at just 55 g ha-1 in spring, aminopyralid controlled seed production and consistently reduced T. caput-medusae cover to near zero. Aminopyralid applied fall was less effective, even at the 245 g ha-1 rate. Unlike spring treatments, fall treatments sometimes reduced cover of forage grasses the first growing season. At final measurement, both spring and fall treatments tended to increase forage grasses, but spring treatments sometimes caused larger increases.