As we will all be aware worms become a problem due to the casts, but what direct issues do the casts cause?
🌿 They may smother the grass plant
🌿 They have a detrimental impact on presentation, particularly when they smear on the playing surface
🌿 They may encourage mole activity
🌿 They create an ideal seedbed for weeds
🌿 If there is a high population, they can create an uneven surface that negatively affects playability
🌿 They can contribute to the capping off of drainage backfill particularly sand bands and slits
❔What can we do to prevent/reduce their impact?
🌿 Cultural
Well timed cultural practices can significantly reduce earthworm activity but are unlikely to eliminate it altogether particularly in clay dominant soils. What actions can we take in our maintenance that can make a difference?
💡 Remove the food source; worms feed on organic matter in the soil and thatch, if these can be minimised as much as possible through scarification and aeration worm populations will reduce in turn. Boxing off grass clippings and collecting leaves helps too.
💡 Reduce soil pH; worms do not like acidic conditions so application of fertilisers or products containing ammonium sulphate, iron sulphate in the autumn or straight sulphur will lower soil pH, however lowering pH can have negative effects in other ways so this approach should be accompanied by soil analysis in early spring to monitor pH levels.
💡 Disperse the casts; this isn’t straight forward on clayey soils and timing is everything, the drier the casts the easier they will be to disperse, and the less smearing will be caused. Brushing, switching, drag matting, harrow raking and rotary mowing can all be effective in the right conditions. Combination grooming tools can be a great tool in the arsenal of groundskeepers in worm cast dispersal.
💡 Surface top dressing; whilst there is little proven direct link between sandy soils and reduced worm cast activity we know that sandier soils are more typically associated with lower thatch and organic matter content and drier surfaces both elements which negatively impact worm populations. Over time amelioration of sand top dressings can help to reduce the severity of casts and crucially make them far easier to disperse.
Chemical
💭 Carbendazim was widely used for worm control but was withdrawn from use in 2017 and its application is now illegal.
💭 Products that are now marketed as approved for worm cast suppression largely consist of soil acidifiers combined with wetting agents that help to reduce casting, however the success of applications is variable and short lived often needing reapplying every 2-3 weeks.
💭 Tea seed meal/saponin based products are not approved for use as worm cast suppressants
