Control of downy brome (Bromus tectorum) and Japanese brome (Bromus japonicus) using glyphosate and four graminicides: effects of herbicide rate, plant size, species, and accession

Authors: METIER, EMILY; LEHNHOFF, ERIK - MONTANA STATE UNIVERSITY; MANGOLD, JANE - MONTANA STATE UNIVERSITY; Rinella, Matthew - Matt; REW, LISA - MONTANA STATE UNIVERSITY

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2019
Publication Date: 11/5/2019
Citation: Metier, E.P., Lehnhoff, E., Mangold, J., Rinella, M.J., Rew, L. 2019. Control of downy brome (Bromus tectorum) and Japanese brome (Bromus japonicus) using glyphosate and four graminicides: effects of herbicide rate, plant size, species, and accession. Weed Technology. 34(2):284-291. https://doi.org/10.1017/wet.2019.112.
DOI: https://doi.org/10.1017/wet.2019.112

Interpretive Summary: Non-native annual brome invasion is a major problem in the semi-arid intermountain west. Herbicide is the most widely used control technique but can have negative effects on co-occurring species. Graminicides, or grass specific herbicides, may be able to control annual bromes without harming forbs and shrubs in restoration settings, but limited studies have addressed this potential. This study focused on evaluating the efficacy of glyphosate and four graminicides to control annual bromes, specifically downy brome and Japanese brome. In a greenhouse, glyphosate and four graminicides were applied at two rates to downy brome plants of different heights (Experiment 1) and to three accessions of downy brome and Japanese brome of one height (Experiment 2). All herbicides reduced downy brome biomass, with most effective control on plants of less than 11 cm and with less than 12 leaves. Overall, quizalofop and fluazifop treatments were most effective, and glyphosate and sethoxydim treatments least effective. Japanese brome and the disturbed accessions of both species were more susceptible to herbicides than downy brome and the undisturbed accessions. These results demonstrate the potential for graminicides to target these annual bromes in ecosystems where they are growing intermixed with desired forage and conservation species.

Technical Abstract: Non-native annual brome invasion is a major problem in many ecosystems throughout the semi-arid intermountain west, decreasing production and biodiversity. Herbicide is the most widely used control technique but can have negative effects on co-occurring species. Graminicides, or grass specific herbicides, may be able to control annual bromes without harming forbs and shrubs in restoration settings, but limited studies have addressed this potential. This study focused on evaluating the efficacy of glyphosate and four graminicides to control annual bromes, specifically downy brome (Bromus tectorum L.) and Japanese brome (Bromus japonicus Houtt.). In a greenhouse, glyphosate and four graminicides (clethodim, sethoxydim, fluazifop-Pbutyl, and quizalofop-P-ethyl) were applied at two rates to downy brome plants of different heights (Experiment 1) and to three accessions of downy brome and Japanese brome of one height (Experiment 2). All herbicides reduced downy brome biomass, with most effective control on plants of less than 11 cm and with less than 12 leaves. Overall, quizalofop- P-ethyl and fluazifop P-butyl treatments were most effective, and glyphosate and sethoxydim treatments least effective. Japanese brome and the disturbed accessions of both species were more susceptible to herbicides than downy brome and the undisturbed accessions. These results demonstrate the potential for graminicides to target these annual bromes in ecosystems where they are growing intermixed with desired forage and conservation species.