Comparing common fountain grass removal techniques: cost efficacy and response of native plant community

Fountain grass ( Pennisetum setaceum ) is a globally pervasive invasive species and a prime example of an escaped horticultural ornamental. In areas where it is not naturally found, it displaces native plant communities and disrupts ecological systems and processes. Cost-effective removal efforts that protect the native plant community are needed for its control. We conducted an experiment from March 2018 to March 2021 in 5 m × 5 m plots to test the efficacy and record costs for common removal techniques (cut and herbicide, herbicide one or two times per year, manual removal) in the Sonoran Desert, Arizona, United States. Each treatment took 2.5 years to achieve control in the plots, and treatments did not negatively affect the native plant community. The response of native plants was mediated by year, such that native cover in treatment plots recovered to similar levels as uninvaded control plots with sufficient rainfall. Plots that received the manual removal treatment had almost five more native plant species than the invaded control treatment (22.7 ± 1.63 compared to 18.1 ± 1.61). Herbicide applied in spring and fall increased efficacy of removals in the first year but was not significantly different from the other treatments averaged over year. Herbicide once per year was most cost effective across different sized areas. Manual removal was also cost effective in small areas (< 0.06 hectares) but was more expensive than herbicide twice a year in larger areas. Our results provide a toolset that enables managers to select removal treatments based on a balance of convenience, resources, and scale of the infestation.