Leatherjackets often eat grass roots and can cause thin patches. Treading on the affected patches when the soil is reasonably dry helps to control them. In a bad attack, the affected areas can be covered with black polythene for about 36 hours and taken off just before dawn to let birds attack the grubs that have come to the surface. This can be repeated.
Birds, such as starlings and crows, often pull out bits of grass to get at the leatherjacket grubs. This damage is minimal and the birds help to control the grubs.
Earthworms are not a pest in gardens – as they can be on golf greens. If casts are considered unsightly, just brush them away. Dogs may foul lawns and cause scorched patches.