Studies show that voles don't enjoy the smell of castor oil, which is what makes it such a useful repellent.
This may not be the right product for you if you're looking for an organic solution - one that's made from all-natural ingredients and doesn't contain any chemicals - but it is worth trying, as they don't like to eat or come near this stuff.
Pros
The safe and gentle solution to driving away voles.
Protects lawn without harming plants or the environment.
Cons
You will need to reapply more often than other products with castor oil as an active ingredient.
You will also need to keep reapplying if rain soaks in, so it's best to use on dry days.