My lawn is covered in worm casts. Is there anything I can do?
Worms are beneficial in the garden as their burrowing activities improve the aeration and drainage of the soil and improve the nutrient content by digesting leaves and other organic matter and passing this into the soil. However in spring and autumn when the soil is warm and moist worm activity can ruin the appearance of a lawn by depositing muddy worm casts across the lawns surface.
To limit the damage caused by worm casts avoid smearing them into the lawns surface by avoiding mowing or walking on the lawn when wet. Wait for the casts to dry out and then brush them away using a stiff brush.
Another option is to deter worms by reducing the amount of food available for them. Remove grass clippings and leaf litter and scarify regularly (NB New turf should not be scarified in the first 12 months.). Earthworms also appear to dislike soils which have a high sand content, probably due to the lower moisture content and abrasiveness of the sand particle. Applying top dressing with a high sand content is one option. Earthworms also appear to dislike soil with a low pH and so the use of acidifying materials in fertilisers and iron sulphate can reduce worm casts.