Some things can help, like giving your parrot its own plants to chew up (like a basil plant) and making sure it has plenty of toys to play with. But in the end, parrots are parrots. The only surefire way to keep them away is to either place the plant in a protective cage, or put it in a room your bird doesn't have access to. Even bitter apple spray apparently doesn't really work to deter our birds!