Test Effectiveness of Different Control Methods on Invasive Buffelgrass

Bean, Travis; Casady, Grant; McClaran, Mitch

Buffelgrass (Cenchrus ciliaris syn. Pennisetum ciliare ), a perennial bunchgrass native to Africa, is rapidly spreading across subtropical regions worldwide, including the Sonoran Desert of southern Arizona and its signature saguaro (Carnegia gigantea) forests and associated wildlife habitat within Saguaro National Park (SNP). C. ciliaris competes with native plants for resources, creates dense stands which inhibit native plant growth and establishment, and fuels fire in a community dominated by plants and animals (such as C. gigantea and desert tortoises) that are not adapted to fire. SNP’s existing C. ciliaris management program has been successful on a small scale but cannot keep pace with the rapidly expanding population of the grass, which may double in infested acreage every 3-5 years. Because C. ciliaris threatens to irreversibly impair the park’s native plant communities and the Sonoran Desert ecosystem, it is essential to expand the knowledge base and available management strategies for C. ciliaris control. The objectives of this study were to evaluate alternative C. ciliaris control measures, including the efficacy of different herbicide treatments, and timing of treatment efforts. We selected individuals from four native plant species plus C. ciliaris in SNP and applied four different herbicide treatments in order to determine the most effective herbicide for C. ciliaris control while minimizing the impact of application on native species. The four herbicides were also tested on the Santa Rita Experimental Range to broaden the scope of inference for the study. Further, the specific impact of one of the four herbicides (imazapic) was evaluated in a greenhouse to determine its pre-emergent properties on a suite of native species and C. ciliaris. We collected plant response data including percent green biomass, number of live tillers per plant, and plant size for the field studies and made counts of emergent seedlings and measured seedling biomass for the greenhouse study.