Keeping the old BlueBerry Patch under control

The farm we bought a few years ago has about a 1 acre blueberry patch on it. It used to be a pick-your-own place. When we bought it they had said it had been about 3 years since they pruned the bushes. We've had the place for 3 years now, so now it's been 6 years since they've been pruned. It's getting hard to walk between the aisles now, and the wild grapes are starting take over. I decided last year I had to prune this year or the bushes were going to start dying from be choked out by the grap vines. Well, I started today, 20 down, a couple hundred to go.

The bushes are very mature, 20-30 years. They produce many tons per season with no care. The birds peck a few during the first week of the season, but after that even the birds get sick of them.

I don't know much about blueberrys. But I know I got a ton of weeds in the ol' patch. The previous owner said they used something called "scat" (I not sure how it's spelled). They said it killed all the vegetation except the blueberries. Does anyone know about scat or anything else people use in their patches? I would really like to maintain this patch and such a weed-control tool would be great. I have no desire to mow between hundreds of bushes [img]/forums/images/icons/crazy.gif[/img]