The mesquite tree/shrub (Prosopis glandulosa) is found throughout the southwestern United States. The mesquite has the capability of restoring nitrogen into the soil like many members of the Legume family of plants. Native Americans used mesquite as a food source and tea (the seeds, however, can be toxic if consumed in too-large amounts).
Today mesquite is considered to be extremely invasive to range lands, home yards and along roadways. Livestock and wildlife easily spread the plant's seeds. Mesquite can quickly form impenetrable thickets.
Kill mesquite in the spring when the buds first appear on the plant by using a herbicide. Soil temperature should exceed 75 degrees Fahrenheit for application of herbicide. Mesquite can be sprayed with herbicide through September but the most effective time to spray is when the buds appear in the late spring.
Mix the herbicide clopyralid with either picloram or triclopyr herbicides. Mix according to the directions on the label for the size of sprayer you will be using. Most mixtures call for 1-2 percent herbicide with water. Many people advocate placing 2 percent dish soap into the mixture to help the herbicide adhere to the mesquite's foliage. Clopyralid can be applied alone without other herbicides but it is expensive and can be mixed with less expensive herbicides.
Spray the mesquite's foliage thoroughly in the spring. The foliage should appear to be visibly wet after the herbicide application--but not dripping wet.
Spray the stem of the mesquite shrub/tree in the height of summer for best results. Spray the trunk from ground level up the stem at least 12 inches. Apply the herbicide all the way around the mesquite's trunk for best results. The trunk should appear wet with the herbicide. If there is dense grass around the base of the mesquite, remove the grass with the herbicide prior to spraying, for best results.
Pull up mesquite seedlings promptly. Use gloves to protect your hands and simply grasp the seedling at the base by the soil and pull quickly out of the ground. Promptly dispose of the seedling.