Lawn grubs can plague your late summer lawn and prevent it from looking healthy. Lawn grubs devour grass roots as their main source of food. Without roots, your grass will quickly die. The most common way to tell if the dead patch of grass in your lawn is caused by grubs is to try to lift it off the ground. If it peels off like a carpet, you have a lawn grub infestation. You will have to reseed the dead area of grass, but you first should get rid of the grubs so they don't destroy more of your precious lawn.
Set up sprinklers and water your lawn to a depth of 1 inch. Do this right before you intend to apply the grub killer insecticide.
Locate a product with the active ingredients of trichlorfon or carbaryl. Read the instructions on the packaging to determine the application rates.
Apply the grub killer over your entire lawn. Spread evenly to ensure the correct amount is applied to your lawn.
Water your lawn again, but this time only water down to a depth of 1/2 inch.
Apply MERIT the following season at the indicated rate. This is a preventative insecticide that will keep grubs from colonizing your lawn.