Hi @chrisbeichert,
It would be difficult to identify the grass while it is still mixed in with the buffalo. Would it be possible to pull some out, with the roots attached, and place it on some concrete so we can see it better?
Unfortunately, grass seeds can lay dormant in the soil and when they experience the right conditions, can sprout up through already established lawns. It looks like it could be Kikuyu, which is not a weed, but it is very fast spreading, and some would call it invasive. If you have a quick google, you will see how frustrating kikuyu can be.
In your case, there is no way to prevent it besides manual removal or painting it with a non-selective herbicide such as Roundup, which will on contact, also kill the Sir Walter. If you can remove it all by hand, this would an option, but if it is a particularly bad infestation, your best bet would be to cut out the section of grass then lay new Sir Walter over the patch.
Have a look at Controlling Invasive Grasses from our supplier Lawn Solutions Australia for some further information.
Jacob
