Dallisgrass is one of the harder weeds to get rid of out there. The root system is so large and goes so deep pre-emergents will not kill existing weeds. It can prevent new patches however. Another issue with dallisgrass is that it can be spread very easily from yard to yard by mowers, wind, birds, along with several other ways. When you see it come up it’s important to start treatment right away. There are two ways to get rid of dallisgrass. The fist way (the back saving way) is to treat each individual crown with Round Up. You must be careful because Round Up will kill the grass around the dallisgrass as well. This way saves you a lot of time and manual labor, but be prepared to look at a dead spot in the yard for a little while until the healthy grass can fill in the spot. The other way you can remove dallis grass is by digging it up. This way takes a bit longer, but you wouldn’t have to wait for the weed to die off. After digging up the dallisgrass, just fill in the area with a little bit of dirt and the grass will fill in the area over time. You need to make sure that you get the entire root system so that it doesn’t come back. Hope this helps!