Grubs can make a smooth green lawn look like a patch-work quilt after they are finished munching away the roots of the grass. You are left with the dried-up dead plants that look like someone burned your lawn. If you take the time to reseed the areas killed off, new growth will quickly fill in the spot, even though it might be a slightly different color of green at first. Donald Lewis, entomologist from the Iowa State University, suggests that you "re-seed or re-sod the damaged areas after soil temperatures warm," which implies waiting until spring--or if in the fall--before the ground gets cold.
Rake away the damaged lawn. This brown stuff will only detract from the clean look of your yard. Use a leaf rake to pull it back and then lift it away into a wheelbarrow or trash bag to dispose into your compost. This dead matter is not diseased and may safely be added to your compost pile.
Rough up the surface of the soil with a garden rake. You only need to loosen the top 1/4 to 1/2 inch of soil for the seed to settle into the surface. If you push the rake back and forth in quick motions, it will dig into the soil and loosen it nicely.
Rake in a handful of high-phosphorus fertilizer like bone meal to promote a healthy root system. You can pick this up from your local garden center.
Sprinkle on a layer of grass seed so that there are about five to seven seeds per inch. The seed should fall into the scratches made by the rake. If you really want to make sure they have good soil contact, sprinkle a fine layer of topsoil over the area.
Water the area three or four times a day. This will keep the water at the surface of the soil where the grass seed is laying and will keep it moist until it is able to send down roots to get its own water from deeper in the ground. Continue watering until you see the grass is about 2 inches tall, then water once a day.
Mow the new grass carefully after it is about 3 to 4 inches tall and water only during very dry times.