There are plenty of ways to prevent the spreading of Bermuda. The most effective way is to cover the border with a plastic wrapper. It will stop the sunlight instantly and stop spreading Bermuda unexpectedly. Another way you can follow is to use gravel around the area to stop the spread of Bermuda. First, cut a trench around the premises by 5 inches. Then fill-up the trench with 2 to 5 mm gravels. It will stop the grasses from spreading their roots, and you will block the complete spreading.