Winter is definitely the best time to kill Kikuyu from your Buffalo lawn, (and Couch, or Zoysia grass too). Kikuyu remains active in many different areas of Australia, whilst the other grass types almost stop growing. Kikuyu can rapidly overtake a lawn if not kept in check. Should you have even a trace of Kikuyu, you need to do one of the 3 steps below for the next couple of winters, until the Kikuyu is eradicated. In the event the Kikuyu gets too thick in Buffalo, the ultimate way to get rid of it is kill the entire lawn and start again, thus it is worth taking the following advice.
1) Kikuyu can be mass sprayed out from Zoysia or Couch by professionals with specialist chemicals, however this isn't posible with Buffalo turf. If you are a commercial lawn maintenance contractor, then the best chemical to work with is DSMA to take out Kikuyu in Couch and Zoysia. It will often require a few applications, over a few months. It's not a one spray option. A new herbicide called Tribute will be launched soon, and at a recent seminar I heard that this used in combination with DSMA has a lot better results taking out Kikuyu. They spayed with DSMA first, then followed up later with two applications a few weeks apart of Tribute. The correct application and combination increased the kill of Kikuyu to 98%.
2) In Buffalo, the only real answer is spot killing Kikuyu with Round Up. Which means you can only get Round Up on the plant you desire to kill, and must not get any on the lawn you want to keep. There are three ways to do this (Note this can also be done for Couch and Zoysia turf).
a) Spray the spot exactly where the Kikuyu is, while being aware that the patch that's going to get the Round Up on it will die. This will kill the Kikuyu, but also some of the good guy grass around it. The disadvantage in this is you will have large dead spots till the lawn regrows, and that can take some time in winter. Probably safer to wait till early Spring to do this.
b) In Winter, after letting the Kikuyu get taller for three weeks with no mowing, a greater alternative is to paint the Kikuyu utilizing a paint brush, making sure you get none on the grass underneath. The ultimate way is to get a section of cardboard, and put it under the Kikuyu, and paint the Kikuyu with Round Up. The cardboard will stop the Round Up accessing any of the Buffalo lawn. You may wish to do this again in 3 weeks, as some Kikuyu might be missed.
c) Again after letting the Kikuyu get taller compared to the rest of the lawn for 3 to 4 weeks, grab the runner in your hand, and inject Round Up with a needle into the runner of the Kikuyu. Ensure you DO NOT stab or inject yourself. Inject each runner in a few spots. You may have to do this again in 3 weeks, as some Kikuyu might be missed. The advantage of this is that you get absolutely none on any of your Buffalo lawn.