Moles are small mammals, 4 to 7 inches long, that live underground in tunnels that they dig with their big front paws. The tunnels are unsightly on the lawn, and gardeners are afraid the little pests are eating the roots of their plants.
The truth is that, yes, the tunnels are unsightly on a beautiful front lawn. They make the ground soft and hard to mow. And if you have a little dog as I had, it may be even more unsightly. My little dog would dig up the runs, looking for the varmint. When he got through the lawn was really a mess!
As for eating the plant roots, they do not. These creatures are strictly carnivores. They do not eat plant material at all. They dine on earthworms, grubs, Japanese beetles, millipedes, ants, and other small invertebrates, many of which do feed on our plants. I don't like them eating the earthworms, but other than that, they probably do more good than harm in the garden. Their digging aerates the soil and we can certainly do without the grubs that eat our plants.
I had one that actually made a tunnel in my raised okra bed--under the row of okra! But not one plant died. He left on his own after running head-on into the wooden side of the bed.
Still, I don't want these creatures in my garden, but I will not kill them. They can be persuaded to go elsewhere with non-lethal remedies. My favorite is to make a small hole in a run and drop in some used cat litter. Cats are predators and moles will not stay around if they are aware of a cat.
Another way to deter them is to collapse their tunnels. Just walk on them. However, that doesn't guarantee that they won't dig another one. You could spend all summer walking on tunnels. A good way to get your garden plowed!
I found a recipe for repellent on the internet using 2 tablespoons of castor oil, 2 tablespoons of dish detergent in a gallon of water sprayed in the mole run. This must be reapplied every 2 or 3 days. Not something I wanted to do.
The best deterrent for a backyard gardener is to plant vegetation that the moles hate. Our old standby, marigolds, as well as daffodils and alliums, the onion family, exude chemicals into the soil that are unpleasant, if not lethal. to garden pests of all ilks.
Tuck the marigolds into your vegetable beds. The low growing ones are best so they don't compete with the crop for water and nutrients. I have always put marigolds in with my tomatoes to prevent damage by hornworms and aphids. Plant them among the other vegetables also
Make a border of daffodils around the vegetable garden. And, of course, plant onions, chives, leeks, and other allium plants.
Voles are a different story altogether. Voles will eat you plant roots.
Voles are also called meadow mice or field mice. They are little with little tunnels that you probably won't see. What you will see is the holes that they have dug. You will also see your plants die if they get in the garden. You could poison them or trap them. You can discourage them with the castor oil spray. They also don't like marigolds, daffodils, and alliums.
But the best way to control voles is to have an outdoor cat!