To use castor oil to get rid of voles, combine 6 ounces of castor oil and 2 tablespoons of liquid detergent in 1 gallon of water, then dilute this mixture using a ratio of 1 ounce for each gallon of water. Spray this mixture on the lawn. A gallon of this diluted mixture sprays 300 square feet of lawn, states Greenview.
Castor oil rids a lawn of voles because the smell repels them, but it does not harm the voles. Spraying the castor oil mixture directly into vole tunnels may increase the effectiveness of this solution, advises SFGate. However, the voles may come back after the smell dissipates, according to Greenview. Castor oil should not be regarded as a permanent solution, and repeated spraying might be necessary.
Sinking glass jars into vole tunnels is another way of controlling these pests. When the voles fall into the jars, remove them to another location. To discourage voles from tunneling into garden areas, place sharp objects in the soil, such as gravel or commercially prepared mixtures. A more permanent solution for getting rid of voles is placing traps inside their tunnels, reports Greenview. These are available from home and garden centers, and professional pest control companies also use them.