Bitter compounds are not effective; gophers have few bitter receptors in their mouth, making them relatively insensitive to bitter substances. Some predator odors have been tested as gopher repellents and show some promise. Commercially available sonic devices are claimed to repel pocket gophers; there is, however, no scientific supporting evidence. The plant known as caper spurge, gopher purge, or mole plant (Euphorbia lathyrus) and the castor-oil plant (Ricinus communis) have been promoted as gopher repellents, but there is no evidence of their effectiveness. Worse, there is much evidence that both plants can become invasive weeds in certain areas. Additionally, these plants are not recommended as both are poisonous to humans, pets, livestock, and other nontarget species. Ricinus is regarded as one of the most poisonous plants known to humans.
Resources (online):
Pocket Gopher
Pocket Gopher Control
