Project Number: 5364-31610-004-01
Project Type: Reimbursable

Start Date: Jun 01, 2008
End Date: May 31, 2012

Objective:
Crested wheatgrass stands in the western United States are often stable in near monocultures and resist invasion by native plants. Attempts to increase diversity in these stands will require management practices that cause a reduction in crested wheatgrass so that other seeded species can become established. Glyphosate is a systemic herbicide that has been used, with variable success, to reduce crested wheatgrass competition with seeded native species. Research with perennial weeds has shown that application timing for glyphosate and other herbicides is an important consideration (Mitchell et al. 2007). Herbicide application is more efficacious when it coincides with photosynthate translocation to below ground perennating tissues. Spring tillage or grazing disturbance may also improve glyphosate efficacy by reducing carbohydrate reserves in the crested wheatgrass crowns. By reducing carbohydrate reserves in the plant crown in the spring, herbicides may be better delivered to the perennating tissues because the carbohydrate sink is stronger than if the reserves had not been depleted.

Approach:
Experiments will be conducted to determine whether: (1) glyphosate efficacy differs among combinations of crested wheatgrass physiological state (timing of application) and disturbance, and (2) establishment of seeded native plants is improved when crested wheatgrass control treatments are more effective. Documents Reimbursable with Forest Service. Log 36518.