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Identification

Earthworms encompass a large group of soil dwelling worms in the phylum Annelida. The most common species found in turf are in the family Lumbricidae including the nightcrawler, Lumbricus terrestris. These worms are brownish-red and grow up to a few inches long. Their bodies are cylindrical with about 150 segments. In turfgrass, earthworms are primarily seen at night or when they are driven out of the soil by watering. Where high populations of earthworms are present, small mounds, or castings of fecal matter, are deposited on the soil or lawn surface.

Hosts

Earthworms may be found in soils under all turfgrass species.

Damage

Earthworms are not pests of turfgrass and do not feed on turf. Earthworms swallow soil as they burrow and feed on microorganisms and partially decomposed organic matter in the soil. Their role in a lawn is primarily beneficial. Thatch buildup has been associated with reduced earthworm populations. Burrowing helps to mix some of the nutrients in the soil together as well as decompose organic matter in the soil. Earthworm activity improves aeration, increasing water and nutrient movement through the soil. Earthworms deposit castings when they ingest soil and leaf tissue and emerge from the soil surface to remove fecal matter. Castings are rich in nutrients and organic matter and can provide some benefits to turfgrass plants. However, when casting piles become large, they may be considered unsightly and over time may make the lawn lumpy. Occasionally, moles may burrow in lawns with high earthworm populations to feed on them.

Monitoring information

Look for small mounds or castings on the soil or turfgrass surface. Earthworms often rise up to the soil surface or sidewalk after a rain or irrigation.

Management

Rake castings to remove them. Power raking with a thatching rake adjusted so the teeth will drag through mounds but not down to the turf crowns will be more effective than hand raking. Adjust your irrigation schedule so the top layer of soil dries out between irrigations. This will drive worms deeper into the soil. Turf mowed at the higher end of the recommended height may hide castings. Earthworms have some natural enemies such as ants, centipedes, birds, snakes, toads, carabid beetles, and nematodes. Do not apply pesticides to control earthworms.