Earthworm
Lumbricidae
Earthworms are beneficial soil movers, but their surface castings on lawns can be seen as a nuisance rather than a genuine pest problem.
Earthworms are soft-bodied, segmented invertebrates ranging from about 2 to 20 cm long depending on species and maturity. They are usually pink, brown or reddish, with a smooth cylindrical body made up of visible rings (segments). There is no separate larval stage; young worms hatch from small cocoons in the soil looking like miniature versions of adults and grow gradually to full size.
They live in the soil and thatch layer beneath lawns, garden beds and mulched areas, feeding on decaying organic matter, dead roots and soil microbes. Some species burrow deep and bring subsoil to the surface, while others stay near the surface layer. They are most active, and most visible, during mild, moist weather in autumn and spring, and retreat deeper during hot dry summer periods or cold winter spells.
Earthworms are not classified as a plant pest in the way insects or mites are. They are one of the most beneficial organisms in garden and turf soil, aerating the ground, improving drainage, breaking down organic matter and cycling nutrients. Their presence is generally a sign of healthy, biologically active soil.
The main reason gardeners look for earthworm control is cosmetic: surface castings (small mounds of worm-processed soil) on lawns can look untidy, feel bumpy underfoot, and occasionally smother fine turf grasses if castings are heavy and left undisturbed. Management is usually about reducing the surface impact rather than eliminating the worms themselves, such as light topdressing, brushing or mowing to break up castings, and improving surface drainage so castings dry and disperse more quickly. Broad-spectrum soil pesticides are best avoided, as they harm the wider population of beneficial soil organisms along with earthworms.
How to identify
- Surface castings: small, soft mounds or coiled ropes of fine soil on the lawn surface, most noticeable after rain or irrigation.
- Uneven or bumpy turf: castings can make mowing patchy and give the lawn an untidy, lumpy appearance if not brushed in or dispersed.
- Slightly smothered patches: in extreme cases, heavy casting build-up can smother very fine or low-cut turf grasses.
- Confirming earthworms: dig a small section of moist soil or turf and look for the worms themselves, or water a small area and watch for worms surfacing, similar to the soap-flush method used for other soil pests.
- Lookalike issue – African black beetle or other soil grubs: these cause root damage, wilting and dead turf patches rather than surface mounds; peeling back affected turf will reveal white or cream grub-shaped larvae rather than segmented worms.
- Lookalike issue – ant nests: ants also create small soil mounds, but these are typically drier, granular and often have a visible entry hole, unlike the moist, worm-cast mounds.
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