Football Pitch FAQ 19. What can I do about earthworm casts?
The main physical activity is to use a drag brush (typically 1.8-2m wide plastic bristled brush) or power brush (such as the Redexim Top-brush, which is a 3x2m wide PTO driven rotating brush) when the casts are dry as this helps disperse them.
Scarification, with the use of a powered sweeper afterwards to remove arisings, can also be considered, especially where there is a lot of surface organic matter and thatch present as these are food sources for earthworms.
For cultural controls consider the use of fertilisers which provide a more acidic soil reaction (in contrast to more neutral reacting fertilisers), the application of granulated sulphur to help acidify the soil surface, and regular light top-dressings of sand to help maintain a drier surface from which it is easier to disperse casts. Boxing off clippings can help remove a food source for earthworms, although this is not always a practical consideration to carry out for many pitches.
Solid tine aeration might be considered as a means of creating air passages in which the soil is more likely to dry. This is because a larger soil profile surface area has been exposed to the drying potential of air, in contrast to a soil profile without an abundance of tine holes.
Earthworms are only active near the surface when conditions are moist to wet, otherwise their bodies will dry out and they will die, and also when the ground is not frozen or very cold. The amount of moisture retained by a soil will depend on soil texture, so heavier clay loams will typically be more susceptible than sandier soils. Their activity is limited to spring and autumn in particular, mild winters and wet summers, although surface activity is often limited if not non-existent during most of the summer.
For several years now, and up to and including 2022, there has not been an approved pesticide-wormicide for the control of earthworms.