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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
Earthworms may be found in soils under all turfgrass species.
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.
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.
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.