What Kills Grubs?

White Grub Test

• White grubs can cause patches or entire yards to die out. You can tell the extent of your grub population by cutting out a 1-square-foot area of lawn with a masonry trowel or spade. Lift up the piece of sod and check the soil for grubs. If there are less than 10 grubs per 1-square-foot area, refrain from using pesticides. For yards that have over 10 grubs per square foot, treat your grub problem in the fall.

Cultural Treatment

• Allow your lawn to dry out in June and July to dissuade beetles from laying eggs in the yard, as recommended by the University of Kentucky. Furthermore, dry soil conditions reduce the chance of eggs surviving. Irrigate your lawn with periodic soakings in August and September. By watering during these months, you help the grass recover from grub damage. In fact, some lawns can tolerate up to 20 grubs per square foot when routinely watered, according to the University of Kentucky.

Chemical Treatment

• Gardeners may use pesticides that contain active chemicals such as trichlorfon or carbaryl to treat their grub problem. Imidacloprid may be used when applied before April 15, according to the University of Rhode Island. Gardeners may be tempted to use pesticides in the spring when their grub damage is highly visible. However, the University of Rhode Island reports that these treatments are not effective because the grubs are large and the damage has already been done to the yard.

How to Apply

• Mow your lawn and rake out dead grass, so that the pesticides can become absorbed into the soil. Remove thatch that is over 1/2 inch thick. Thatch is the layer of dead and living organic matter between you grass blades and soil. Rent a dethatcher to remove the thatch. Spray the lawn with the pesticide and water immediately. Give your lawn 1/2 to 1 inch of water, according to the University of Kentucky.