There's a product called "Milky Spore" that kills JB grubs before they emerge. It's a bacterial application, so totally safe and organic. I believe you apply it to lawns/gardens in the fall or early spring and it kills the grubs. I can buy it here at the farm supply store, but it's also available on Amazon. you might want to check that out. A friend of mine used it and said it worked very well, better than traps because traps actually lure beetles into your garden.