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Dr Ian Plummer

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Lawn Care
Removing Worms from Lawns



  1. The Problems
  2. The Benefits
  3. Worm Control
    1. Curing the Symptoms
    2. Discouraging Worms
      1. Acidity
      2. Worm Extraction
    3. Killing Worms
      1. Chemicals
      2. Other
  4. Additional Information
Common earthworm - lumbricus terrestris
Earthworm (lumbricus terrestris) and worm cast

Please do not write to ask "where can I get these products from?"  The market changes too quickly and governments continually remove effective chemicals from the market. Be aware that groundskeepers have access to professional chemical supplies, which require training to use safely. 

1 The Problems

Worm Casts
Worm Casts

Worms produce worm casts (small piles of digested earth), which are unsightly, slippery, blunten lawn mowers, affect play on sports turf (e.g. bowls, croquet and golf) and make balls, etc. unpleasant to handle. 

The casts also can act as seedbeds for weeds. The action of worms can also facilitate weed growth by pulling down seed material from the surface.

Worms are a source of food for birds and animals, many of which are undesirable on sports or fine turf.  Birds leave droppings and can damage the turf through pecking.  Burrowing animals, such as moles, can destroy huge areas of expensively maintained turf in their search for worms.

2 The Benefits

Worms aerate the soil through their motion improving its structure and process waste material (e.g. components of thatch).

"Castings are digested animal manure and plant matters and have five times the nitrate, 11 times the potash, seven times the phosphorous and three times the magnesium of the soil around them."
http://www.azcentral.com/home/garden/articles/0302worms02.html [dead link]

3 Worm Control

3.1 Curing the Symptoms

Use of a switch to remove dew and worm casts
Switching turf, courtesy https://www.bmsproducts.com/ - Turf Care Section

Worm casts can be removed mechanically by brushing, switching or using a drag mat.  Brushing is only feasible for small areas. Switching involves using a long switch, like a fishing rod, the end of which is swept quickly over the surface of the grass.  Telescopic ones, 4-6m long, with a thin fiberglass tip are available and large areas can be covered quickly.  Whilst primarily intended to break-up morning dew they smash or smear the worm casts.  A drag mat enables large areas to be processed.

Whilst this overcomes the immediate problem, the worm casts will be there next morning. The alternatives are to discourage, remove or kill the worms. Worms are not necessary for a healthy lawn; they do nothing unique.

3.2 Discouraging Worms

Earthworms prefer a near-neutral soil acidity (pH), moist soil conditions and plenty of plant residue on the soil surface.

3.2.1 Acidity

Worms do not seek soils with high acidity (low pH = acid).  There are products that intentionally acidify the surface of the soil which claim to drive the worm down from the surface.  The acidifying agent needs reapplying at 2-4 week periods. 

I would raise an eyebrow at this approach.  Grass, like worms, has a preferred pH range (see diagram on right) and the viability of the grass is likely to be affected if its conditions are modified.  There are grasses however which like acidic conditions, but they may not offer the required turf properties, e.g. hard wearing, drought resistance, etc.   Also, if you pour something on the top of soil and are reapplying it frequently, where does it go to?  Down seems the obvious answer so the worms get driven further and further down?

The Croquet Association advises in its publication 'Croquet Lawns: Their establishment, improvement and maintenance', section 58:

"As the pH drops towards 5.5 the spraying will become less necessary. The cheapest way to lower the pH is to apply Calcined Sulphate of Iron at ¼oz (7gm) per sq. yd."

Example products: 'Worm Clear Plus' (spray) and 'Sulphur Worm' (granules). The product 'CastClear' (2010) claims to deter worms - its principal component is ammonium thiosulphate, hence liberating sulphur and acidifying the soil.

Grass and pH range

3.2.2 Worm Extraction

Chemical: Various solutions can bring worms to the surface where they become prey to birds and other predators, sweeping machines and lawn mowers.  The following quotes should act as pointers.  Searching Google for ' permanganate vermifuge -koi -fish -aquarium ' etc. can pull up information on the use of permanganate excluding reference to its use on fish.  A vermifuge is something that flushes worms out. Solution strengths are infrequently quoted.

"The efficiency of mustard as a vermifuge for estimating earthworm populations or collecting earthworms for laboratory studies was compared with that of formalin, potassium permanganate and household detergent. Mustard was shown to be as efficient as potassium permanganate and both these substances were better than formalin. Household detergent was an extremely poor vermifuge. Mustard does not kill earthworms as does potassium permanganate, and unlike formalin it is not carcinogenic and does not have phytotoxic effects on clover. Mustard would therefore appear to be an ideal "environmentally friendly" means of estimating earthworm populations and, for collecting healthy worms for laboratory studies in areas where soil sampling is not feasible due to the damage it would cause."
http://biology.bangor.ac.uk/research/publication/A1992HW93900001 [link defunct]

"Worm extraction (vermifuge, a chemical irritant to bring them to the surface) from soils is possible with formalin, (now probably an illegal use), with liquid detergents (4 liters per 50 x 50 cm quadrat (many worms die)), potassium permanganate solutions, and probably least destructive or harmful to surrounding conditions is a with a mustard solution 25 ml per liter."
http://fwie.fw.vt.edu/rhgiles/aRuralBusiness/AlphaEarth.html [link defunct]

Potassium permanganate is a powerful oxidant and its storage is a concern.

Electrical: There are a few mentions of electrical 'worm probes' or 'worm harvesting', primarily used by fishermen to bring worms to the surface. For example:

"Electric Worm Harvester: The electrical current produced by the Harvester will bring the Worms to the surface. If the current is strong enough it will stun the Worms who will recover without harm. If the current is too strong it will injure the Worms and white spots will show on the skins. Such Worms may live up to 24 hours but will die, or the Worms may remain in the ground and die."
http://www.oldphoneman.com/FSMagnetos.htm [link dead]

Beware however!

"CPSC is aware of more than 30 deaths involving functionally-identical worm probes. Consumers have been electrocuted by contacting the exposed metal shafts and shocked by touching the ground in the vicinity of the probe."
Example: https://www.cpsc.gov/id/recalls/1991/pm-worm-probes-found-hazardous-electrocution-risk-cited-in-cpsc-order-to-halt-manufacture-and-sale-of-worm-probes

3.3 Killing Worms

3.3.1 Chemicals

The posh term for a worm-killing chemical is a vermicide. As indicated in the caveat at the head of this article the chemicals available to you depends where you are and who you are. Some products may not be available to members of the public. The Royal Horticultural Society (UK) states:

"Pesticides for the control of lawn pests are no longer available to home gardeners. Pesticides marketed for professional use cannot be used on garden lawns, although it is possible have them applied to sports turf, such as a bowling green. In that type of situation it may be worth employing a contractor who has the necessary Certificate of Competence to use professional pesticides on amenity turf." (link now removed by RHS)

I used to quote trade names but the products were successively pulled from the UK market: hence I do not give advice on products, suppliers or usage; please do not ask! As an example, the first chemical below was banned in 2003 and the second will be banned in 2006:

"As far as we are aware, thiophanate-methyl and carbendazim are the only 2 active substances used to control worms. Under 91/414/EEC, thiophanate-methyl is to be included in Annex I as a fungicide (although the Directive has yet to be published). A decision has yet to be taken for carbendazim under 91/414/EEC."
(defunct: http://www.pesticides.gov.uk/guidance/industries/pesticides/topics/pesticide-approvals/eu/eu-reviews/worm-control-products)

For information on banned chemicals in the UK see http://www.hse.gov.uk/pesticides/topics/pesticide-approvals/pesticides-registration/withdrawal-and-restrictions/banned-and-non-authorised-pesticides.htm

Use the Internet to track down products available in your region given the active ingredients.

The good news is that there are products that are not sold specifically as vermicides, but do reduce the worm population.  Typically fungicides, which are routinely applied to sports turf, have this beneficial side effect.

The following quote gives indications of some chemicals which are effective at killing worms.  NOT ALL OF THESE ARE SUITABLE FOR SPRAYING ON GRASS - SOME ARE HERBICIDES AND WILL KILL IT!  Caveat Emptor!

"Earthworms prefer a near-neutral soil pH, moist soil conditions, and plenty of plant residue on the soil surface. They are sensitive to certain pesticides and some incorporated fertilizers. Carbamate insecticides, including Furadan, Sevin, and Temik, are harmful to earthworms, notes worm biologist Clive Edwards of Ohio State University.(4) Some insecticides in the organophosphate family are mildly toxic to earthworms, while synthetic pyrethroids are harmless to them.(4) Most herbicides have little effect on worms except for the triazines, such as Atrazine, which are moderately toxic. Also, anhydrous ammonia kills earthworms in the injection zone because it dries the soil and temporarily increases the pH there. High rates of ammonium-based fertilizers are also harmful."
http://www.attra.org/attra-pub/soilmgmt.html (no longer working) and  reference 4 is Edwards, Clive A., and P.J. Bohlen. 1996. Biology and Ecology of Earthworms. Chapman and Hall, New York. p. 426

The following quote gives a comprehensive list of chemicals (and their trade names) that will kill worms. NOT ALL OF THESE ARE SUITABLE FOR SPRAYING ON GRASS - SOME ARE HERBICIDES AND WILL KILL IT!  Caveat Emptor!

"University researchers identified other toxic chemicals that home owners and lawn services may use [to kill worms]:

  • 2,4-D
  • acephate (Orthene)
  • azinphosmethyl (Guthion)
  • bendiocarb (Turcam)
  • benomyl
  • captan
  • carbaryl (Sevin)
  • carbendazim
  • carbofuran (Furadan)*
  • chloropicrin
  • copper sulfate
  • cypermethrin (Ammo, Cymbush)
  • D-D fumigant
  • diazinon
  • endosulfan (Thiodan)
  • esfenvalerate (Asana)
  • ethoprop (Mocap)
  • fonofos (Deafened)
  • malathion
  • metam-sodium (Vapam)
  • methomyl (Lannate)
  • methyl bromide
  • metribuzin (Sencor, Lexone)
  • nicotine
  • paraquat
  • parathion
  • phorate (Thimet),
  • thiophanate-methyl (Topsin-M)

http://www.azcentral.com/home/garden/articles/0302worms02.html [link dead]

"Earthworms were killed with a pesticide (carbofuran) which is known to affect earthworms at various rates depending on the species and the type of soil (Lee, 1985). Due to the low hydraulic conductivity in vertisols, we chose to apply high doses of 10 kg ha−1 a.i. The product   (Trademark Furadan) was spread on the soil surface every 2 years."
http://www.mpl.ird.fr/SeqBio/Archives/FichesPerso/Articles/Tiphaine/chevallier_ASE_01.pdf [dead link]

Example products: Rigby Taylor sells "Systemica" fungicide/vermicide containing carbendazim. http://www.rigbytaylor.com/Shop+by+Product/Chemicals/Worm+Control/Systemic+Worm+Cast+Control+5lt_0632102-05.htm. Look also for "Mildothane Turf Liquid" (contains thiophanate methyl). Scotts Turfclear contains carbendazim - http://www.aitkens.co.uk. These will become impossible to find as the bans become effective - search Google for  ' "worm control" fungicide ' (Oct 2005).

3.3.2 Other

There do not appear to be any biological controls on the market for earthworms. Moles are not an option!

Disclaimer: Whilst I have attempted to gather useful information and provide pointers, I make no representations about the accuracy of the information quoted. Please do not email to ask "where can I buy products?" - use the Internet!

4. Additional Information

Peter M Taylor writes about the above.

"An interesting and comprehensive article on the Oxford website which doesn't seem to highlight the key points.

Worms are beneficial to lawns and will always be present they are just an inconvenience when working at surface level which needs to be discouraged.

The best means of discouragement is the regular removal of the plant residue by verticutting and scarifying gentle within the season i.e. down to soil surface and severely into the underlying soil ideally in the Autumn.

Damp surface conditions also need to be discouraged by sarel (gentle spiking) rolling during the season and deeper spiking and possible verti-draining to remove compaction outside the season.

The use of lining marking products raises the pH (alkaline) encouraging worms and they should be used sparingly especially towards the end of the season.

It would be a rare situation where repeated acidic chemical applications to lower pH are required and pH may be lowered by regular applications of topdressing of know alkalinity."

Peter Howells has approached (UK) suppliers:

a) Aitkens Sportsturf Ltd, 01977 681155, have a product for worms called Ringer. 1 x 5Ltr Ringer (5Ltr treats 12,500 sq.mtr) £130.90 per 5Ltr + vat and carriage (2005). http://www.aitkens.co.uk

b) You can use a chemical called Carbendazim to prevent worm casts forming. It is found in products such as Scotts Turfclear, but this only comes in 5 Litre sizes. However Nu-Turf produce a product called Nu-Turf Worm Control which contains carbendazim and it comes in 1 Litre sizes and costs £33.00 + delivery + VAT. (2005)

Both products are restricted and must be applied by qualified personel.

Sweepfast Ltd. 01675 470770, The Homestead, Old Kingsbury Road, Marston, Sutton Coldfield, West Midlands, B76 0DP, https://www.sweepfast.com

Mark Homan adds [Aug 2007]

The recent correspondence about worm casts reminds me that back in September 2005 I reported:

1. Success with Carbendazim for worm suppression. I think this is now no longer an approved product, but that is not to say it is unobtainable. Old stock is still around!

2. On the subject of a preponderance of worm casts around boundary lines and the effect of lime in the liner in encouraging coarse grass I stated: 'I have done some research on.... white liner. It appears that the usual products have a PH of about 8.5. However, there is one called Elite which at 7.7 is still high, but breaks down and releases the lime more slowly so has less effect in raising PH. Also it is claimed the lines last much longer. Arsenal and Chelsea both use it.... I am going to try switching to Elite ..... and will report the results sometime next season'.

I did not in fact report the results last season as I felt that the trial was too short for the excess lime already in the soil to dissipate. Well, after two years it has. I now no longer have dark thicker grass along the lines nor any more worm casts than elsewhere on the court. Pros and cons I have observed are:

Pro: Better grass/less casts as above It seems to last longer. Hence a saving in liner and labour.

Con; Elite is more expensive than most alternatives. It is stickier than other products and clings to the lining equipment. If you wash it out this is wasteful of liner and labour. If not the box eventually gets clogged up. Whether on balance it is therefore more or less economical I cannot say.

Also remember, this is a subjective opinion based on the particular soil conditions of one court and the extremes of weather in the last two summers.

Brendan Quinn, a pharmacist and a member of Birdwatch Ireland, notes [2011]

* Furadan also known as carbofuran is a banned Eu substance and has been linked to deliberate bird poisonings, as it has been today in Ireland. Probably best not to list it in products used to control worms.

Stan Daurio notes [2012]

In paragraph 3.3.1, you say that 2,4d will kill worms.  As part of the massive Canadian and U.S herbicide 2001-2010 recertification program, 2,4d was found safe for mice, rats, dogs, rabbits, crayfish, ducks, earthworms. honeybees and many others included in the comprehensive studies; you may want to reference the findings of the Pest Management Regulatory Authority of Health Canada for more information.
30/05/2012 20:39:55

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Updated 16.vii.17
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