How to tell if your lawn has grubs

Grubs feed on your lawn throughout the summer. It is important to tackle grubs early in their life cycle before they cause damage. The damage will become visible in later summer and by then there may be permanent damage to your lawn. Grubs attract other pests such as skunks and opossums. These animals will dig up your lawn while scouting for grubs. Recognize the signs of a grub infestation and take care of the problem as soon as possible.

Instructions
Keep an eye out for brown, uneven patches on your lawn are visible signs of grubs. The damaged sod will easily peel away from the rest of the lawn. Predatory animals, searching for grubs, will leave tunnels and holes in the lawn.

Make a quick map of your property. On the map, divide your property into high priority and low priority areas. Note areas of past grub infestations as high priority. Highly visible areas may also be considered high priority. Low priority areas are areas that you would like to test but are less concerned about appearance and potential damage.

Look for grubs. In high priority areas use a bulb planter to remove dirt every ten feet. Pour the dirt onto a plain piece of cardboard. Count the number of grubs on the cardboard and note on your map. To get the amount of grubs per square foot, multiply the number of grubs on the cardboard by ten. In low priority areas count the grubs every twenty feet. Knowing the amount of grubs in your lawn will allow you to determine the appropriate treatment.

Replace the dirt. Use a watering can to saturate the area.

Source: http://www.ehow.com/how_5620130_tell-lawn-grubs.html#ixzz342L2jdvg