Not their beneficial activity of aerating the soil, but the detrimental effect of their casts on the surface of your lawn.
There are about 27 species of worm in the UK but only three create worm casts at the surface of your lawn
Earthworm cast is made up of soil and worm’s digestive system secretion. Final product is very slimy and if left on the lawn, can later be smeared across the lawn from mowing or even walking on the lawn. Earthworm casts also create bumps in the turf and can quite often be unsightly.
The vast amount of earthworm casts can quickly turn your lawn into a patch of mud.
Leaves do attract worms to the surface. Worms pull leaves into their burrows to feed on these later.
One simple thing you can do to discourage worms from coming to the surface is to clear autumn leaves immediately.
Leaf clear up service
That will limit the amount of casts on your lawn .
Other methods include:
- Use of an acidifier
- Spraying with a fungicide like: carbendazim