Put 3 cups of table salt into a pot. Add 6 cups of water and place the pot on the stove.
Turn the stove burner on high and bring the salt mixture to a boil. Mix the solution with a spoon until the salt melts. Turn off the stove and remove the pot.
Allow the mixture to cool for a few minutes and pour it into a garden sprayer. Place the lid on the garden sprayer and turn it clockwise to close it. Pump the handle on top of the sprayer up and down to pressurize the salt and water mixture.
Put on work gloves to protect your hands from yucca's pointy leaves. Cut off each leaf about 4 inches from the tip.
Prune off any blooms that are open or spent to reduce the spread through wind, water and wildlife. Gather the cut pieces and dispose of them. This process exposes the living tissue of the plant for better absorption of the salt mixture.
Cover nearby desirable plants and grass with plastic sheeting to protect them from salt spray.
Sprinkle salt around the base of the yucca plant next to the main trunk.
Spray yucca with the mixture in the garden sprayer starting at the top of the plant. Thoroughly soak the plant on the cut portions and underneath the leaves until the solution drips off.
Remove the plastic sheeting from nearby vegetation.
Reapply the salt solution weekly until the yucca dies. Dig up the dead yucca and dispose of it.