Lawn grubs are small, curved insects that are white, brown or brown with a white head. These pests are immature beetles, and they feed on the roots of turf, causing the grass above to turn brown. Dead areas in a lawn can be caused by many things, but it is easy to determine if it is caused by grubs: Simply pull back the grass and look for them. Although small, it only takes ten grubs per square foot to brown a lawn. Once you spot grubs, take immediate steps to kill them.
Choose a pesticide formulated for killing grubs. Diazinon and Imidicloprid take up to three weeks to work, leaving the grubs more time to do damage, but they are long lasting and effective. Dylox, on the other hand, kills quickly but does not last long.
Wait for a hot, dry day in late July with no wind. Water the lawn thoroughly, then apply the pesticide as per the instructions on the package. Use slow, even strokes, and make sure to cover every part of the lawn. If the pesticide does not come with an applicator, use a broadcast spreader for granules or a pressure sprayer for liquid. One application should be sufficient to kill the grubs.
Water the lawn again. A slow, deep watering will ensure that the pesticide seeps low enough to kill the emerging grubs. Keep children and pets off the lawn for two or three days.