Municipalities are considering alternatives to traditional herbicides for suppressing weeds and vegetation in areas frequented by the public. Two field experiments were conducted to test the efficacy of alternative nonselective herbicides: one in Corvallis, OR, on a mixed lawn of perennial ryegrass, annual bluegrass, and broadleaf weeds, and another in Las Cruces, NM, on a predominantly bermudagrass lawn with broadleaf weeds. The experimental objective was to quantify and compare the effects of repeated applications of 10 nonselective herbicides to terminate a lawn with mixed vegetation. Applications were made every 2 wk for four applications starting on April 15, 2022, in Corvallis and on May 26, 2022, in Las Cruces. Data collected included the percent green cover over time calculated using an area under the percent green cover progress curve (AUPGCPC), the percent green cover at the conclusion of the experiment, and the changes in monocot and dicot densities over the course of the experiment. All treatments resulted in a lower AUPGCPC compared to water only, except for mint oil + sodium lauryl sulfate + potassium sorbate. The only treatments with average percent green cover <50% were ammoniated soap of fatty acids + maleic hydrazide (47% green cover) in Corvallis and pelargonic acid (38%) in Las Cruces, suggesting that more applications would be needed to terminate the lawn under similar circumstances. At the conclusion of the experiment, the water-only plots averaged 90% and 93% green cover in Corvallis and Las Cruces, respectively. The changes in monocot and dicot densities over the course of the experiment indicated that some of the products tested may be more sensitive to dicots, or, in some cases, monocots, suggesting a potential for future selective herbicide research in certain locations and climates.

Nomenclature: Ammoniated soap of fatty acids; maleic hydrazide; mint oil; sodium lauryl sulfate; potassium sorbate; pelargonic acid; annual bluegrass, Poa annua L. ‘POAAN’; bermudagrass, Cynodon dactylon (L.) Pers. ‘CYNDA’; perennial ryegrass, Lolium perenne L. ‘LOLPE’