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1 October 2013 Effectiveness and Cost of Downy Brome (Bromus tectorum) Control at High Elevation
Amy L. Concilio
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Downy brome (Bromus tectorum) is an invasive, annual grass that has spread through much of the Great Basin desert but remains patchy at high elevation. This study evaluates control options for outlier infestations in the eastern Sierra Nevada, CA, based on their ecological effectiveness and their economic and practical feasibility. I tested the efficacy of hand-pulling, sheet-mulching, and soil solarization followed by broadcast and seedball seeding of native forbs and grasses. Downy brome cover, density, and dominance in the seed bank decreased with all removal treatments. Soil solarization and sheet mulching were most successful at eliminating downy brome (decreasing density by 99% after just 1 yr of treatment in both cases), but they had negative nontarget impacts on other herbaceous species. Germination of native seeds was low with both broadcast and seedball seeding, probably because of dry conditions. Each of the methods tested has potential for decreasing or eliminating small-scale, outlier infestations of downy brome along roadsides and in disturbed sites and thereby helping to contain the invasion.

Nomenclature: Downy brome, Bromus tectorum L.

Management Implications: Downy brome is an invasive, annual grass that has spread through much of the Great Basin desert, with significant effects on native species. Control of downy brome is particularly challenging because of its impacts to the fire cycle. At the high-elevation extent of its range, however, it remains patchy, and native plant communities are still relatively intact. Removal of these outlier infestations could reduce downy brome spread, prevent future impacts on the fire cycle, and help conserve native sagebrush–steppe habitat. I tested the ecological effectiveness and the economic and practical feasibility of several control options for downy brome infestations at the western edge of the Great Basin desert, including hand-pulling, sheet-mulching, and soil solarization, followed by broadcast and seedball seeding of native forbs and grasses. Hand-pulling led to significant reductions in downy brome cover, reduced its dominance in the seed bank, and increased forb cover. Downy brome was virtually eliminated after both soil solarization and sheet mulching, but these treatments had negative impacts on other herbaceous plants. Reseeding efforts were unsuccessful, likely because of low soil moisture availability. Based on my results, I would recommend hand-pulling for controlling downy brome in areas where the native seed bank remains relatively intact, such as along hiking trails adjacent to undisturbed plant communities. Soil solarization and sheet mulching would be better options for use along roadsides, pack stations, and in other disturbed areas. Each of these control methods is relatively low technology, safe, and, thus, appropriate for volunteer groups, which could decrease costs of implementation. Proactive investment in containment of downy brome invasion at range margins could have significant economic and ecological benefits into the future.

Weed Science Society of America
Amy L. Concilio "Effectiveness and Cost of Downy Brome (Bromus tectorum) Control at High Elevation," Invasive Plant Science and Management 6(4), 502-511, (1 October 2013).
Received: 25 January 2013; Accepted: 1 June 2013; Published: 1 October 2013

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