Grubs are larvae of scarab beetles that feed on roots of pasture and turf grasses, causing them to turn brown as they draw out moisture and nutrients, and eventually die. These destructive white lawn pests cause your lawn to look unsightly, with brown spots or patches all over it. Unless you kill the grubs and repair your damaged lawn, they will spread and feed on the entire grassy patch. The extent of repair required depends on the amount of lawn damage.
Douse the patches of your lawn damaged by grubs in water. Allow a garden hose to water the area deeply and thoroughly for 10 to 15 minutes, or turn sprinklers on for an even soaking.
Insert a shovel into the soil around damaged grass and lift it up to remove it. Put it in plastic bags and dispose appropriately.
Loosen 5 to 6 inches of soil with a shovel or rake. Turn it up to break compacted soil and aerate it, and remove any white C-shaped grubs that appear as you work.
Add a layer of compost or rotted manure to the soil and rake it in so it mixes with the existing soil well. Also follow label directions to mix a grass-seed starter fertilizer to the soil.
Purchase good quality grass seed and spread it over the affected patch by hand if it is small, or with a seed spreader if the damaged area is large. Work toward an even distribution, but do not worry about overseeding a particular spot. Also sprinkle seeds into healthy grass around the damaged area to ensure the absence of bare spots once the new grass grows.
Rake the seeds to lightly cover them in soil and ensure good seeds-to-soil contact. Cover the area with straw so the delicate seeds do not blow away with the wind or rain, or are chewed by birds. This is especially important if the damaged area is on a slope.
Water the seedbed frequently, two to three times a day, until the seeds germinate and the grass establishes itself.