Many greenkeepers find worm casts frustrating because they are unsightly and result in muddy, slippery turf during wet conditions, which can affect ball roll. However, worms provide huge benefits to turf meaning it’s important to manage casts without damaging the worm population.
Our technical expert, Dr Colin Mumford, explains that there are no legal controls to eradicate worms. But, there are things greenkeepers can do to manage them, while reaping the rewards they bring to the soil.
What are worm casts and why are they a problem?
Only certain worm species produce casts on the surface. The three main species are Lumbricus terrestris (common worm), Aporrectodea caliginosa (grey worm) and Aporrectodea longa (black-headed worm).
Worm casts are small mounds of highly nutritious excrement found on the turf surface and are a side effect of worm activity below the ground. The mounds contain highly active biological material such as bacteria, enzymes and plant and animal material, all of which are hugely beneficial for the turf.
Why are worm casts such a problem for greenkeepers?
- Make the courses look unsightly
- The course can become muddy and slippery, affecting ball roll
- Weed seeds can establish in the soil masses left behind by worms
- Worms attract predators such as moles and birds
Worm casts are generally harder to manage in wet and cold conditions because the soil is harder to disperse. If you have heavier soils, then this problem is exacerbated because the soil smears across the surface rather than breaking down.
The benefits of high worm populations
Dr Mumford says that worm casts need managing on golf courses, but in a positive way.
This is because they provide many benefits to the turf that can help reduce turf stress, improve turf quality and reduce input requirements, providing a cost saving for greenkeepers.
Benefits of worm populations:
- Recycle nutrients and bring them to the surface so they are available to turf plants
- Breakdown organic matter which helps to release nutrients to plants
- Aerate the soil, allowing gaseous exchange to take place
- Improve the soil structure, providing channels for drainage
Top tips on managing worm casts
Because worms are hugely beneficial to soil and plant health, it’s in greenkeepers interest to manage them carefully.
There are several cultural practices available that can help to minimise course damage from worm casts:
- Disperse the soil mounds (casts) by:
- Brushing or switching the turf canopy - only do this if the soil mound is dry otherwise it will smear on the surface
- Fitting scrapers to rollers on mowers to prevent build-up on the rollers
- If the course is dry, pull a dragmat, brush or upturned chain harrows across the surface
- Apply sand only top dressings – this can help increase the sand content of the soil, meaning the casts have a higher sand content and are therefore easier to breakdown
- Worms prefer neutral-to-slightly-alkaline soils, so changing the pH can deter them. To do this use a sulphur-based fertiliser. Be careful not to reduce the pH too much as this will slow down microbial activity and organic matter break down
We know worm casts can be a bit of a headache at this time of year but remember all of the good work worms are doing under the surface, to help keep your turf healthy and stress-free.