Earth Worms

Earthworms have an important role in helping to aerate soils, reducing compaction, improving water penetration and infiltration rates, processing organic matter and reducing thatch.
Earthworms come to the surface under moist soil conditions (e.g. in late autumn and winter) and retreat downward in dry weather.
However, some species of earthworms leave casts on the turf surface and this has many negative effects:
* Aesthetics
* Uneven surface levels
* Weed invasion more likely as casts may bring dormant weed seed to the surface or by wind blown seeds landing on casts and geminating.
* Mole activity increase in proportion to worm populations.

Approach

Reduce thatch in programmed approach to minimise food source for earthworms.
Minimal use of organic amendments.
Lower soil surface pH to discourage earthworm activity by using acidifying fertilizers.
Encourage drier surfaces through aeration and verticutting etc.
Minimise amount of clippings returned to soil (organic material) by use of slow release fertilizers and/or Plant Growth Regulators.
Using a wetting agent with strong penetrant activity will ensure that moisture moves from the surface and down the soil profile and make surface casting less likely.