Spring Glyphosate Application for Selective Control of Downy Brome (Bromus tectorumL.) on Great Basin Rangelands

Abstract

Downy brome has converted millions of hectares of Great Basin rangelands from shrubland to annual grass-dominated systems. Methods for removing downy brome from sites that already have perennial grasses established are especially needed because of the difficulty in re-establishing perennial species. In this study, early spring applications of glyphosate alone and glyphosate plus imazapic were monitored for 2 yr. Cover of downy brome was reduced from 45 to 10% by spring application of glyphosate alone and to approximately 1% with the addition of imazapic. Perennial grass cover was not affected by the spring application of glyphosate. The addition of imazapic reduced perennial grass cover in the first year; however, it recovered by the second year. The selective response to glyphosate may be due to differences in growth stage or dormancy characteristics between annual and perennial species. Our findings suggest spring application of glyphosate may provide an alternative approach for managing annual grasses on Great Basin rangelands.

Integrated Management of Cheatgrass (Bromus tectorum) with Sheep Grazing and Herbicide

“…Glyphosate was not effective in our study in contrast to Espeland [27] and Morris [11], which may be attributed to the abundant B. tectorum seedbank at our site, where B. tectorum had been the dominant species since the fire break was established in 2012 [35] and no control action had been implemented. Bromus tectorum, which is capable of both fall and spring germination [46], may have emerged after herbicide application.…”

“…Espeland et al [27] determined that a low dose of glyphosate applied in spring and fall did not harm native grasses and reduced B. tectorum cover in the first year after spraying, but a second fall glyphosate application failed to reduce B. tectorum cover or seed bank. Morris et al [11], however, determined that spring-applied glyphosate alone reduced B. tectorum cover for two years, and combining with imazapic provided even greater control. Imazapic has been widely used [28][29][30][31] because it provides residual soil activity, which is important for controlling annual plants such as B. tectorum, with early post-emergent fall application recommended [29].…”

“…Glyphosate, imazapic, and rimsulfuron are commonly used herbicides for managing B. tectorum [26], and while these herbicides have varying levels of selectivity, applying them when native plants are dormant minimizes their impact on desired vegetation [11]. Espeland et al [27] determined that a low dose of glyphosate applied in spring and fall did not harm native grasses and reduced B. tectorum cover in the first year after spraying, but a second fall glyphosate application failed to reduce B. tectorum cover or seed bank.…”

“…Another approach is timing herbicide application to take advantage of different phenological stages of the weedy and desired species; ideally herbicides are applied when the desired species are dormant reducing off-target damage. For example, Morris et al [11] determined that a spring application of glyphosate reduced the cover of cheatgrass (Bromus tectorum L., also known as downy brome) and had no effect on native grasses because of differences in growth stages or dormancy. Typically, managing weed populations to restore desired species is extremely difficult, and many populations persist despite repeated control efforts [12].Another approach to alter the trajectory of a community and manage undesired species is targeted grazing with livestock.…”

Evaluating winter annual grass control and native species establishment following applications of indaziflam on rangeland

“…Furthermore, very few herbicides for use on rangeland or in natural areas provide S. cereale control. Glyphosate can be used during native species dormancy to provide POST control of overwintering winter annual grass seedlings or for broadspectrum weed control before revegetation on sites without desirable species (Kyser et al 2012(Kyser et al , 2013Morris et al 2016). Although the use of glyphosate can be effective for short-term control, glyphosate has no soil residual and does not provide protection against reestablishment of invasive grasses (Sebastian et al 2017b).…”