The best way to kill fleas and chiggers in a lawn is to clean up the lawn then apply a spray pesticide that contains premertrin, diazinon, cyflurhrin and/or carbaryl. These chemicals kill pests but do not harm the grass. Reapply the pesticide after two weeks to kill any flea eggs that may have hatched.
Applying pesticide primarily to hot spots and areas that pets frequent yields the best results. To find areas of the lawn with high densities of fleas and chiggers, walk around the yard in a pair of knee high, white socks. Watch for fleas jumping onto your socks as you walk, and take note of the highest-density areas.
Cleaning the lawn makes it less desirable for fleas and chiggers and removes possible hiding spots. Clean up any yard debris, remove brush and cover trash cans. After this, mow the grass to a short height.
Make sure to wear gloves, goggles and a mask while applying the pesticide. Have family members and pets wait indoors during the application. Make sure that no one goes onto the lawn during the manufacturer-recommended waiting period; this is typically around two hours. The wait time should be indicated on the pesticide's label.