As children we’re often taught that earthworms, far from being horrible yucky wriggly things, are in fact beneficial to our gardens. Indeed there is some truth to this, they help break down organic matter, they aerate the soil, and they improve lawn drainage. That said, for the lawn enthusiast earthworms are more of a nuisance than a blessing from nature, the organic by products expelled by worms, known as worm casts, create muddy areas on top of the lawn, which can spoil it’s appearance and encourage the growth of weeds. Worst of all, earth worms are the primary food source of moles, and are therefore directly responsible when moles make an appearance on your lawn.
Optimum conditions for worms
- Heavy clay type soils, high in organic matter and thatch, both primary food sources for worms
- Alkaline soil
- Damp and warm conditions that bring the worms to the surface and increase the problem of worm casts. Frosts, though normally detrimental to a lawn, can have the benefit of driving worms underground to warmer temperatures
Chemicals and fungicides exist for commercial grass care operations such as on sports grounds, although these are not generally available to the public, there are however other steps that you can take to control the activities of worms in your lawn should you wish to.
- Remove thatch and other organic matter – go through the usual scarifying and reseeding process during the autumn, and also make a point of collecting up any fallen leaves that would otherwise break down and provide an endless supply of worm food
- Raise the cutting height of the mower
- Remove worm casts with the aid of a brush or drag mat to improve the lawn’s appearance
- Lower the pH of the soil using iron sulphite based fertiliser. This is a more aggressive approach and isn’t for everyone, bare in mind that this product is strong and can stain clothes and pathways.
Despite these tactics, being completely adapted to living in soil makes earthworms tough to evict from your garden altogether, especially if you find yourself completely overrun by them.
Second only to the earthworm, crane fly or daddy long legs larvae, known as Leatherjackets are the proverbial wriggly lawn pest, and although they are less common than earthworms they can be even more damaging when they do strike.
Typically Leatherjackets appear in late summer when crane fly lay their eggs on the ground where they may go unnoticed by you for several months. When the larvae hatch they proceed to feed on the grass roots, and you’ll see the evidence of this come spring when distressed yellow patches appear on your lawn, or you notice birds pecking at the ground to feed on them, which in itself damages the lawn.
Prevention of Leatherjackets
The presence of crane fly in your garden, a very wet winter, and birds pecking at the ground in early spring are all tell tale signs that you might have a Leatherjacket problem looming. Therefore the application of insecticides, particularly those containing HCH, in the autumn will go a long way towards preventing problems in the spring and summer. If you forget to do this then you can use a nematode (worm) insecticide can be used to kill the larvae later on in the year.
Less common than Leatherjackets, but more of a problem to deal with, Chafer grubs are the larvae of the Chafer beetle, and once it lays its eggs in the early summer the larvae will be increasingly more damaging to the soil until they finally leave as fully grown adults in the spring time. Some species of Chafer grub live on compost heaps and along borders, although these are not considered to be pests.
Like Leatherjackets, the damage from Chafer grubs is usually characterised by yellowing patches of grass that is weak at its roots. What can be more damaging is the activity of foraging animals such as birds (particularly crows, jays, and magpies) and also badgers and foxes as they dig the grubs out of the soil.
Like Leatherjackets a course of nematode based insecticide can be used to kill Chafer Grubs if you suspect they might be present on your lawn, and being vigilant to the activity of animals on your lawn is the most useful way to determine if they are present.