Lawn chiggers are the larvae of mites -- specifically of the Trombiculidae family. When in their larvae stage, the chiggers feed on the skin of humans and animals. These tiny bite marks look like small, red welts that typically cover the softer areas of skin like the stomach, arms and backs of the knees. Because they are so small, most people only realize they have an infestation when they notice the bite marks on their body. Although you can thoroughly wash your clothing and sheets to rid your body and home of chiggers, that won't help the fact that your lawn is infested. To get rid of chiggers altogether, you'll have to treat your lawn with sulfur.
Mow your lawn and pull weeds on a regular basis as chiggers live in overgrown grass and weeds.
Fill a pillowcase halfway with powdered sulfur.
Tie the top of the pillowcase in a knot.
Drag the pillowcase through your grass in a row-like pattern. The fine powder escaping through the pillowcase will provide a light dusting of sulfur -- just enough to repel and kill the chiggers but not enough to ruin or kill your grass.
Repeat in the spring, fall and any time you notice you have chigger bites.