If left untreated, moles can spread quickly throughout the lawn and cause a lot of damage. Moles can destroy your yard quickly, so that's why it's so important to control the situation before it becomes a bigger problem. If you think your lawn has a mole infestation, you need to take action quickly. Moles can damage plant root systems, your green lawn, mowers, and sprinkler systems. Repairs can cost upwards of $2,500.