Foxtail is an annual weed that grows all over the United States. It usually goes unnoticed in lawns until the summer, as in the spring it looks like light green grass. When the seed heads appear in July, however, the weed becomes conspicuous. Even though foxtail grass is an annual plant, each plant produces hundreds of seeds. As long as these seeds are still in the soil, it is difficult to get rid of the foxtail grass.
Balance the nutrients in your lawn and care for it properly. Foxtail cannot survive in a healthy, well-balanced lawn. Test the soil with a soil test kit and make sure the pH falls within the range recommended for your grass type. Water and fertilize properly as well, taking care not to over-water or over-fertilize.
Apply a pre-emergent herbicide in the early spring before foxtail starts growing. This will prevent the seed from germinating. For foxtail, use an herbicide with pendimethalin or oxadiazon as the main ingredient. Follow the directions on the package for application and safety instructions.
Apply a post-emergent pesticide containing monosodium methanearsonate (MSMA) if the weeds still appear. Follow the directions on the package. You may need to apply this more than once to kill all the foxtail.
Repeat these steps again the following spring. Eventually, all the seeds in the ground will die and the weed will no longer grow. It may take two or three years, however, to eliminate it completely. Keeping the grass thick and strong will go a long way to prevent the return of foxtail.