I'm pretty sure I have a grub worm problem. I'm going to dig up some yard later today to make sure. Assuming that I have an infestation, all the reading I've done to date suggests that trying to get rid of them now is pointless. That the damage is already done, hibernation is setting in, and I should wait for the fall when they start laying eggs again to get rid of them. I'm hoping to confirm this is the case but if not, I would like to know the best way to get rid of them.
Way back in the past when we had a lawn we had a similar problem. If it's what we call leatherjackets then there is something you can do now. In the evening put down a piece of plastic over the area. Overnight the grubs will come out of the grass and up to the surface. Morning comes and you take off the plastic and leave the birds to have a feast. Repeat frequently - word gets round the birds that a great food source is on offer. It won't cure the dead bit of grass but it might take out some of the next generation of the horrible beasts.
Solar Station Construction Plans by Ben Peterson -- ebook