If your lawn is full of large brown patches, you may have a grub infestation. These tiny insect larvae are tenacious and can be difficult to kill without the use of chemical pesticides. Fortunately, there is a natural method to rid the lawn of grubs. By changing some of your lawn care habits and attacking the grubs with some natural predators, you can eliminate these pests without chemical control.
Treat your lawn with spreadable Bacillus popillae, a small bacteria that will attack and kill the grubs but will ignore other beneficial insects, like bees. It is also not harmful to people. You can sprinkle this on your lawn any time the ground is not frozen, although it works best in spring and fall. The bacteria will defend your lawn for 10 to 15 years after being placed in the soil.
Let some beneficial nematodes loose. Like Bacillus popillae, you can get beneficial nematodes at your local home and garden store. Spray them on your lawn and they will attack the grubs, spreading grub viruses and eating the carcasses.
Water your lawn as little as possible. While this may seem counterproductive, since you may feel like you are parching your already-stressed grass, in reality less moisture prevents grubs from hatching. If possible, do not water your lawn at all in the spring.
Keep your grass high. This will keep Japanese beetles from landing in it and laying eggs that produce the grubs in the first place. Cut your lawn 2 to 4 inches high.