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Worm activity is most evident on lawns but can also be a nuisance in gravel paths.
Symptoms
Worm casts. Photograph copyright Dorling Kindersley Deposits of mud (worm casts) are found on the surface of lawns, and are particularly noticeable if the turf is of fine quality. The casts become smeared by lawnmowers and feet, making the turf muddy and slippery. Moss and weeds can develop on these muddy spots.
Worm casts are produced mainly during September to October and March to early May when the soil is warm and moist, and also in spells of mild weather during the winter. Worms remain close to the surface under these conditions. When the soil is dry or cold they go deeper into the soil, resulting in less deposition of worm casts on the surface.
Cause
Allolobophora species of earthworms are responsible. These worms feed on decaying vegetation in the soil and they deposit their muddy excrement on the lawn surface. Earthworms can have beneficial effects in lawns as their burrowing activities help in aerating and draining the soil. They also incorporate organic matter into the soil by pulling dead leaves into their tunnels.
Control
Disperse worm casts when they are dry, with a besom broom or an up-turned wire rake moved from side to side. However, there are often few days during the autumn to spring period when worm casts are sufficiently dry for this to be an effective solution.
Earthworms are less abundant in very acidic soils, but while it is sometimes possible to reduce the pH of soil by adding sulphur dust, it is unlikely that soil could be made sufficiently acidic to completely deter earthworms.
Pesticides for the control of lawn pests are no longer available to home gardeners. Pesticides marketed for professional use cannot be purchased or used by amateur gardeners , although it is possible to have them applied by a contractor who has the necessary Certificate of Competence to use a professional pesticide approved for use on amenity turf.
