Mounds of Dirt in Lawn from Earthworms

Q. Our Bermudagrass lawn is covered with little "mounds" of dirt. Something is digging in or digging out of the dirt and I suspect it can't be good!  Grubs?  What do I do? 

Mounds of dirt created by earthworms in a lawn

A. These mounds appear in lawns after a long rain or if the soil has been flooded. Those mounds of dirt are excavations from earthworms. Earthworms move to the soil surface when they can’t get enough air, leaving behind little piles of dirt. We also see it in soils that are compacted for the same reason.

earthworm channel

            There are many earthworms in our soils particularly where plants are growing. They provide a lot of benefit to the soil and recycle nutrients from decaying plants and very small animals like insects. They also create air and water channels in the soil.

            Earthworms do not like to be exposed but they will come to the surface if they can’t get the air that they need. The only way they do that is by digging these channels to the open air. In some parts of the country earthworm populations are so dense they create problems when they surface, leaving behind the piles of dirt you’re seeing. In cases like these, people are more likely to ask how to get rid of earthworms.

            In your case, don’t worry about it. It’s a good sign. These mounds will disappear after a few more things. If the problem persists and it does bother you, aerate the lawn with a commercial core aerifier and dethatch it.