White grubs eat the roots off of your turfgrass in the spring and fall of the year. If you see symptoms of yellowing turf in spots around your lawn - you may want to check for white grubs by cutting out a one square foot chunk of sod and rolling it over. If you count more than 10 to 12 white grubs under the sod you will probably want to treat your lawn for white grubs. The grubs are approximately one inch in length and have a "V" pattern on the anus.