If you see irregular brown patches in your lawn, you may have a grub problem. Grubs are insects in the larvae stage, and they dine on the roots of turf grass, causing it to wilt and die. To diagnose a grub infestation, dig up a patch of grass in a suspect area. If you see a white, beetle-like creature rolled up in a C-shape, you've got grubs. There are a few proven ways to eliminate these creepy crawlies, such as spreading nematodes or milky spore on a troubled lawn.