Lawn Problem: Worm Casts

How do I identify worm casting?

Worm casts are small deposits of soil on the surface of the lawn. You will most likely see them in spring and autumn when the soil is moist.

What are worm casts?

Worm casts are the waste material excreted by some types of worms on the lawn surface. This material is nutrient rich.

There are only a few varieties of worms that cast on the lawn surface in this way, but in big numbers, they can cause real problems. The castings are deposits of soil. If these are left or walked on or mowed over, they smear and create small pockets of capped soil which grass cannot push through. This leaves unsightly areas upon the lawn.

How do I cure worm casting?

There is no real way of controlling worms or their casting on lawns. Carbendazim was traditionally used to irritate the worms and send them deeper into the soil profile rather than coming to the surface. This product has been withdrawn from the market. I mention it here as we are still often asked about it. LawnsOne does not use any products but instead prefers management of the lawn to reduce the impact of worm casting.

Worms feed on organic matter particularly leaves at the lawn surface, so removing these regularly take away part of their diet. If the weather is favourable and the casts dry out, they can be raked or brushed to break them up and disperse them. If the weather remains wet, you may have difficulty mowing and the casts maybe turned into capped soil areas. As long as the grass gets a good spring feed with good growing conditions these areas will fill back in quite quickly. Some remedial action is maybe necessary on severely affected lawns.

Key points to remember

  • Clear all debris and leaf litter off your lawn regularly.
  • Disperse the casts when conditions allow.
  • Keep mowing whilst the lawn grows

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