Yuccas are shrublike plants with tall green foliage and large cream colored flowers that tower over the plants during the summer months. While considered a pleasant addition to the home garden by many, especially for its southwest appearance, yucca plants can become invasive, especially the "list-leaf" yucca variety. It is best to control yuccas in the following manner in the spring and summer, and when the plant is dry.
Mix herbicide and vegetable oil (or diesel fuel, if desired) together in a pump garden sprayer or a backpack sprayer. Use 1.5 parts herbicide and 8.5 parts vegetable oil. Texas A&M University Cooperative Extension recommends Remedy as the herbicide, and the vegetable oil they found that mixes well with Remedy is JLB Oil Plus. Alternatively, a premix herbicide and oil is available called "Remedy RTU."
Place a 100-mesh screen valve behind the nozzle of the garden or backpack sprayer. This will help prevent the mixture from dripping from and/or clogging the valve.
Shake the mixture well before applying.
Spray the yucca plants for two full seconds over the center of each "whorl." A whorl is the individual sections of the plant whose leaves share the same root stem. Repeat when you need to again control the spread or growth of the yuccas.