MSU Extension Invasive Plants
Monthly Weed Post, October 2024
Integrating spring glyphosate application and spring seeding to establish bluebunch wheatgrass in cheatgrass-infested rangeland
Introduction
Range and pasture severely degraded by cheatgrass is often managed by combining herbicide and seeding. However, cheatgrass can outcompete seeded species due to its winter annual life cycle—it emerges in fall, overwinters as a seedling, and resumes growth in the early spring. Seeded species, in contrast, usually emerge in the spring, immediately facing a size disadvantage to already-growing cheatgrass. Strategically timing herbicide and seeding treatments based on the biology and ecology of cheatgrass and seeded species could improve restoration outcomes. For example, controlling cheatgrass with glyphosate, a non-selective herbicide with no soil residual, in the fall or prior to seeding in the spring would allow seeded species one season of growth before the next cohort of cheatgrass emerges the following fall, thus shifting the size advantage in favor of seeded species.
Methods
We tested glyphosate application timing (fall or spring) and five bluebunch wheatgrass seeding dates (1 fall, 4 spring) on cheatgrass-infested rangeland at two sites in western Montana. A 2% glyphosate solution was applied on 15 October 2017 or 11 April 2018. Bluebunch wheatgrass was seeded in late October 2017 or once every two weeks starting in early April through mid-May 2018. We sampled density and cover of bluebunch wheatgrass and cover of cheatgrass in summer 2019 and 2020, the first and second growing season after treatments were applied.
Results and Management Implications
Spring seeding of bluebunch wheatgrass following a spring glyphosate application generally improved bluebunch wheatgrass establishment, increasing its density and cover compared to fall glyphosate application and fall seeding or spring glyphosate application following fall seeding. Density of bluebunch wheatgrass was highest in the first three spring seeding dates – 3 April, 19 April, and 4 May – averaging about 35 plants per square meter. Seeding in the fall (30 October) resulted in about 10 plants per square meter. Bluebunch wheatgrass cover was 7 to 14% across the first three spring seeding dates combined with spring glyphosate application. Invasive plant managers can integrate a spring application of glyphosate with spring seeding of bluebunch wheatgrass. Spraying and seeding could occur days to weeks apart, as long as glyphosate is applied prior to bluebunch wheatgrass emergence. Glyphosate is non-selective, though, so this approach should be reserved for range and pasture that have little to no remaining desired vegetation. Read the entire article by Majeski, Simanonok, Miller, Rew, and Mangold. This research was supported by a grant from the Montana Noxious Weed Trust Fund.
