Summer Grass.when and how?

. to eliminate. I have patches through my lawns up to about 1200mm diameter, tho mostly 750 - 900mm.
I seem to remember there is a specific spray, but is applied mid winter when the summer grass is not apparent. How best to mark the patches, and what is the spray?

Mrs B here. Depends what has caused it. its great to develop a "programme" to care for your lawn. We have a front yard with a 250 year old tree in it, that literally sucks the life out of our lawn. So I use a fertilizer twice a year (granuals). I check for grass grub twice a year and use the prills sparingly on the areas with the grubs, again, twice a year. I also use a product like Turfix (I use a generic one from good old warehouse) to knock out everything bar the grass. All these things or any one of these things I look for and use sparingly when needed. Some years its just a bit of fertiliser, some years its the whole hog. If you find out exactly what is causing the patches, you can use just the product you need. In our case it was grass grub. I have a friend who is a landscaper and he spotted it by raking over the dead areas, and pointing out the grubs at the very edge of our lawn in those areas. He advised me to only use the very expensive prills on the areas infected and it worked beautifully. Its not a huge lawn but its really nice now.

what do you mean by summer grass ?

It's a very coarse, erect grass, that is only apparent over the summer months. A wider leaf than normal lawn grasses, regrows rapidly after mowing. Seems to die down over winter and become unrecognisable, but springs back early summer. Tends to spread in a circular manner, and in patches until it eventually takes over an area. Has a less significant and shorter rhizome to Kikuyu. Sends up quite solid but shortish flower/seed stalks.

got a pic?

the problem with most grass type weeds is they are difficult to remove without killing the good grasses.
there used to be a selective spray that did some but its not available to home owners due to being very toxic.
only way would be to roundup the weeds and reseed the patches.

Do you mean paspalum?

I'm guessing it is summer grass that is referred to, not paspalum or anything else, a grass which appears in summer and dies off over the colder months. It is quite flat and each plant can spread to over 30cm wide, killing out the good lawn grasses so large dead patches turn up in a lawn, quickly to be filled by other weeds. I found out last week that there is a specific spray to deal to summer grass but was not able to get it's name, even if I did I'm told it is very costly and you may find that home gardeners are unable to purchase it.
Try approaching Farmlands, golf courses, or business' that deal with turf if you want to know more or you could google.
Once rid of it good turf management should keep it at bay in your lawn. My 3yr old lawn is well managed and I have only found about 6 plants in that time

i found this http://pestweb.co.nz/?pesttypes=summer-grass

That looks very similar. I see there are some other varieties too.
I see it is not actually a rhizome but a rooting node that it can slowly spread by. As it is in a domestic lawn, regularly mown, I doubt seed becomes set.