According to the University of Missouri, castor oil creates a barrier that repels moles and gophers. According to a study by the Michigan State University, castor oil repellent works on 25 of the 26 lawns tested. Castor oil repellents come in liquid and pellet forms and have different formulations, depending on the brand. Generally, castor oil pellets last between one to three months per application. To maintain effectiveness, apply the pellets regularly.
Load the lawn spreader with castor oil pellets. Generally, 3.75 lbs. of product is enough for up to 2,500 square feet, but check the packaging to determine the proper amount for the particular brand you use.
Run the spreader along the edges of the lawn, then push it back and forth in the area bounded by the treated edges. This method helps you apply the castor oil pellets evenly.
Reapply the castor oil pellets every two months or more frequently in rainy seasons.