Frightening Moles
Some electronic, magnetic, and vibrational devices have been promoted as being effective in frightening or repelling moles. None, however, have EVER been proven effective. Promoters cite "testimonial evidence" only.
Repellents
Some have claimed that castor oil and castor oil products have shown repellent properties. Retired University of California-Davis biologist Rex Marsh has studied mole control systems for decades. When he was asked this question, he replied, "I'm unaware of any published tests of mole repellents here in the West that support their efficacy... I guess because castor oil is distasteful to humans, these repellent promoters believe it is logical that it would be repellent to other mammals. Planting castor beans was suggested many years ago as a method of discouraging moles and pocket gophers from gardens. That too was never proven to be efficacious."
"As you can imagine, mole repellents are extremely difficult to evaluate under field conditions because of the moles' erratic movements about their extensive burrow systems. I'm not convinced that if a mole stops pushing up mounds in my yard for 30 to 60 days that it has been truly repelled. It may be that the mole has moved to the other end of its burrow system, which happens to be two houses away. The cause and effect relationship for repellents is hard to determine with this fossorial animal."
"The expense of mole repellents and the time and energy to apply them repeatedly can hardly be justified when trapping will give such positive control results. As you can determine, I am a staunch believer in traps—Nash choker, Woodstream's spear, and the Out O' Sight."
Thus, beware of claims of efficacy for mole repellents!
Resources: (online)
Mole Control
Mole Publication
