Castor oil will not kill them, but it will upset their digestive tracts. It will also make your lawn less appealing. For a homemade remedy, mix three parts castor oil and one part dish soap.

Is castor oil safe for grass?

A less common use of castor oil is as a garden pest deterrent, applied directly to soil, grass and plants. Castor oil has a distinctive odor and unpleasant, nauseating flavor, but is not harmful to plants.

How do I apply castor oil to my yard?

To use 100 percent castor oil as a mole repellent, you must mix three parts castor oil with one part dish soap. You will need 4 tablespoons of this mixture to add to 1 gallon of water. Once the solution is mixed properly, it will need to be applied evenly to your yard with a spray bottle or sprayer.