The Bureau of Land Management (BLM) and other agencies use tebuthiuron, a soil-activated herbicide, to kill thousands of acres of sagebrush in areas where it grows in dense patches. The chemical pellets sink through the soil and, when absorbed by the plant, prevent photosynthesis.
The idea is to thin the sagebrush and maintain a balance with other native vegetation. The fields of dead sagebrush look very desolate. Read more about it here and here.