Effectiveness of cheatgrass suppression using perennial grasses as a biological control method

Authors: Harmon, Daniel - Dan; Clements, Darin - Charlie

Submitted to: California Fish and Game
Publication Type: Abstract Only
Publication Acceptance Date: 4/27/2021
Publication Date: 4/28/2021
Citation: Harmon, D.N., Clements, D.D. 2021. Effectiveness of cheatgrass suppression using perennial grasses as a biological control method. California Fish and Game. 21:3.

Interpretive Summary:

Technical Abstract: Cheatgrass, an exotic invasive annual grass, is one of the greatest resource management challenges in the Intermountain western United States. Since it’s accidental introduction in the 1880’s, cheatgrass has continually expanded it’s range, providing a fine-textured early maturing fuel as senescence occurs early summer months. This increases the chance, rate, spread and season of wildfire. Wildfires fueled by cheatgrass can burn well over a million acres annually in the Great Basin region. This habitat loss threatens native plant communities and the wildlife and domestic animals that rely on them. The economic losses due to wildfires are catastrophic. A strategic integrated pest management approach is required to effectively control cheatgrass. The best-known method for sustainable control of cheatgrass is through competitive exclusion by perennial grasses. Biological control which often relies on predation, herbivory and parasitism can also be achieved through natural mechanisms such as competitive exclusion. Competitive exclusion is a principle by which two species competing for the same limited resources cannot coexist, leading to the exclusion of the weaker competitor. A mature perennial grass depletes soil moisture and nutrients to the detriment of cheatgrass. Deep tap rooted shrubs and forbs occupy a different niche than the shallower fibrous roots of grasses and do not exclude cheatgrass. At the seedling phase cheatgrass is the dominant competitor compared to a perennial grass seedling. Therefore, cheatgrass must be removed using temporary control means such as herbicides prior to establishing a perennial grass that once mature can then become the dominant competitor. We will present effective integrated methods based on our data to temporarily remove cheatgrass with herbicides and then establish perennial grasses that will effectively suppress cheatgrass, reducing wildfire threats. Our plant material testing research can help determine the most effective perennial grass species for specific management goals including suppressing cheatgrass and increasing forage base.