Grubs look a lot different from earthworms. Earthworms are long and skinny. Most earthworms don’t get fatter than 1/8 of an inch. Grubs on the other hand are only about ½ inch long, and ¼ inch thick. Earthworms tend to eat soil in your lawn and they stay away from your grass. Grub worms on the other hand will eat your lawn and most any other organic material that they find in your grass. If you only have a few grubs, they are not very likely to do a lot of damage. However, if you have a high population of grubs, they will damage your lawn a lot faster than it can repair itself. Most of the time, they do not kill your grass. Your grass is killed as a result of high temperatures or drought after the grubs have gone through and eaten out 80% of the roots. The best way to kill them is to use grub killer. You may want to apply it into applications just to make sure that you kill them.