What Causes Piles of Dirt in Your Yard?

The appearance of mysterious dirt piles in the yard confounds and frustrates even the most knowledgeable home gardener. However, not all dirt piles indicate a serious problem. Some yard invaders simply turn and freshen the soil, while others can cause extensive lawn damage. Dirt piles can range in size from barely noticeable to large and unsightly. Identifying the culprit helps homeowners determine the proper course of action.

The bane of gardeners and landscapers, pocket gophers and moles burrow underground, building mounds at the entrance to their tunnel systems. Pocket gophers feast on plant bulbs, vegetables and grass roots. In their search for grubs and earthworms, moles can leave a yard littered with holes and dirt hills. The least-toxic approach for treatment and prevention of burrowing-animal damage is remove the food source or make the area inhospitable. Using toxic chemicals against gophers and moles can harm pets and other wildlife that come in contact with the chemical or affected animals.

Ants provide beneficial pest control for yards. They feed on insects that cause lawn damage and pose no threat to grass. Ants only become problematic when they deposit soil granules excavated from nests below the ground and those granules grow into hills. Control the number of anthills during nesting season by aerating the soil and scattering a fine layer of dirt over the grass. Adjust the lawnmower to a higher setting and rake anthills frequently.

Earthworms can spoil a beautiful landscape with piles of dirt that result in a rough lawn. However, these creatures actually benefit the yard by aerating soil. Earthworms create dirt piles as they pass through the soil and deposit castings, or excretions, on the grass surface. High in organic nutrients, these castings serve as fertilizer for lawns. Homeowners may notice an increase in earthworm dirt piles during the moderate temperatures and moist periods of spring and fall. Typically, earthworms cause no grass damage unless present in large colonies.

The African black beetle, or black lawn beetle, does the majority of its damage in the larval stage. In the southeastern United States, these young insects wreak havoc on lawns from spring until late fall. They live under the ground and feed on tender grass roots and young shoots. The beetle grubs repeatedly make their way to the surface and crawl back deep into the ground, leaving their signature dirt piles on the lawn. Because the larvae live below the standard reach of chemicals, they can be difficult to treat and control.

People from the South may be familiar with the aquatic crayfish, used in a number of tasty recipes. Also known as crawdads and crawfish, this crustacean has a relative that lives on land and tunnels into moist and water-saturated soils in the Southeast. Terrestrial crayfish pose only a slight threat to grass, but can deposit significant amounts of dirt on top of lawns. Little more than an unattractive nuisance, these seasonal mounds can be leveled with spray from a hose or light raking.