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Contaminated Manure



Following this year's problems with pesticide residue in manure, DOW AgroSciences have created a website - Manure Matters - to provide guidance and advice.

Click here to visit


Proposal for a DIRECTIVE OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL establishing a framework for Community action to achieve a sustainable use of pesticides


As usual my words are in green


Contact with MEP


Question asked of MEP : Linda McAvan

I emailed you earlier in the year about our problems with contaminated manure. Just wondered if you had any idea whether the new EU legislation on pesticide use would affect the use of aminopyralid the herbicide that caused our problems. From what I can find out it would seem not as aminopyralid is supposedly not harmful to humans.


From what I have read I can't understand why farmers are so upset about it as the legislation seems only to apply to chemicals that have proven health affecting issues. It just seems strange that to ban a substance it has to be proven to be harmful as if this is the case how did these chemicals receive approval in the first place. Surely on initial application they would have to have been proven to be safe wouldn't they?


24 February 2009


Thank you for your e-mail regarding the new pesticides legislation which has recently been adopted by the European Parliament and national ministers and whether it could help with your problem of contaminated manure.


These new laws strengthen the existing rules for governing the production, licensing and use of pesticides. One such measure is a new authorisation procedure for plant protection products. This would cover all products containing active substances, safeners or synergists intended for use as a plant protection product. To be authorised, the product must meet a strict set of criteria, including that it shall not have any unacceptable effects on food or plants. It is therefore not limited to health effects. I have attached a copy of the new law, which lists the criteria in Annex II so you can assess whether the authorisation of aminopyralid would be affected.


However, this legislation will only gradually supersede existing EU law. Pesticides that can be placed on the market under current legislation will remain available until their existing authorisation expires. Once the license for aminopyralid runs out, the producers would have to submit a comprehensive dossier with test results showing that it met the strict criteria outlined in the Regulation. There is also the possibility for the public to submit opinions and evidence.


I hope this information is helpful and the new rules are useful for your case.


Conversation with DOW Agro-Chemicals


June 2008

I have just had a very long telephone conversation with a DOW representative who was very helpful, so just to pass on some information obtained.


First of all we need to all be aware that DOW produce aminopyralid which is only one of the herbicides that may potentially be affecting our manure supplies. Dow's name has been given as a source of information to the public as they are the only company of this type with a public helpline and they are happy to field calls or email enquiries. This could mask the fact that the chemicals responsible for our problems may be from different companies and have names other than aminopyralid. As well as herbicides used on grass, chemicals used on wood shavings (typically used for horse bedding) may also have the same affect on our plants. These could be industrial chemicals as well as herbicide related.


Symptoms in plants:

Plants being poisoned by herbicide residue will typically exhibit the spoon shaped leaf growth. If this symptom is not present then it is likely that the problem to plant growth is attributable to another cause.


Health Risks

From tests done on cows ingesting treated silage or grass it has been shown that only a very small quantity of any residue is digested. 98% of the residue passes straight through the cow. As human digestive systems are even less efficient in the digestion of plant material this should be less for us. I am told that there are not carcogenic substances in the herbicide. If manure products are at all suspected of causing tummy upsets it is more likely that these are caused by bacteria present rather than chemicals


Texture of manure

The herbicide does not alter the texture of manure. Any sliminess or strange textures are maybe attributable to how manure has been left stacked. It is possible that manure with this type of look and feel has been stored at the bottom of a pile for a time and that rain etc has washed through the soil causing it to sour. This means that there is less air in the manure and decomposition will be much slower. Residue may also seep down the pile causing a more concentrated build up in this area. It is possible that even if gardeners have bought manure from the same pile that some will suffer worse effects than others due to where their particular manure was within the pile being stored on the farm. This is backed up by our experiences as the areas where we stored manure prior to spreading is the worse affected area. Our manure was stacked for about three months during which time we experienced heavy rain. Other plot holders have had worse symptoms in areas where the manure was stacked too.


Composting of affected plant materials

Affected plant material should not be composted on the compost heap as it is bacteria present in soil that breaks downs the chemicals. Affected crops should be dug back in to the soil. Burning was mentioned earlier but RHS don't recommend this method of disposal. See RHS response below.


Manure too fresh?

The use of manure that is too fresh will not produce the distorted leaf symptoms shown in the case of herbicide damage where the leaves curl upwards like a spoon. Fresh manure affects the roots of plants by burning them and not the top growth. Potatoes may have scabs on their tubers. Plants may also display symptoms of  black leg.


Can residue leach into surrounding areas?

I have checked with the chemical company about the likelihood of residue seeping onto neighbouring plots and they say that once the manure has been mixed into the soil, any leachate is more likely to go into the soil profile rather than sideways. If there is any sideways movement it will be feet rather than yards, and this would only happen with manure on the surface, and torrents of rain.

We have areas on our plot where two plants growing right next to us have one showing damage and the other not - which seems to confirm DOWs answer - that is not yet! Although run-off seems to be another matter whereby particles have been swept downhill of affected areas and caused a problem.


Dow's Notice to Allotment Holders and Gardeners

Dow have published a web page of frequently asked questions with respect to the current problem This is no longer available


Frequently Asked Questions:

RHS Advice

June - October 2008

Question: If veg is growing in land that has been manured using contaminated manure but shows no signs of being affected – is that safe?


RHS answer

Well there is no way you can exclude the possibility of weedkiller being present.  Although the weedkiller is not considered a toxic material and must be present in vanishingly small quantities if plants are not affected there is no data on how safe the produce is to consume.  One might assume the risk to be small but without solid scientific data it would be folly to assert this with confidence


The residue levels will decline in time, though this process is slower in plant tissue than in the soil. Delaying harvesting from affected plants until 2009 is a sensible precaution. For annual crops such as potato, it is best not to recommend consumption.


The PSD say that they are going to obtain samples to test. I wonder if given the nature of how the herbicide residue is released whether this would be in any way conclusive.


PS Date update:

Following PSD update the advice now is that it should be safe to eat vegetables growing in the soil where the manure has been used.


Question: So should we have our soil tested?


The RHS say:

The issue of testing is flawed. Even cases of known contamination have failed to be confirmed by laboratory testing simply because the residue levels are too low to be detected


Question: Apparently courgettes and squash don’t succumb and appear to thrive so are they safe?


RHS answer

Quite possibly but no one really knows for absolute certain.  Because the weedkiller is not considered a toxic material and must be present in vanishingly small quantities where seems little reason to be overly concerned if you have already consumed produce, although clearly if people feel ill they should consult their physician.


PS Date update:

Following PSD update the advice now is that it should be  safe to eat vegetables growing in the soil where the manure has been used.


Question: If affected plant material is burned then is the ash safe to use on crops?


RHS answer

This is not a recommended way of disposing of contaminated plants. The recommended way is to incorporate plant material into the soil so soil microbes can degrade it. The sooner this is done the longer the microbes have to do the job when the soil is warm and moist.


Question: So should we be asking for compensation?

John from Sandwell has been advised by his National Society of Allotments and Leisure Gardeners  representative that a reasonable compensation calculation is  2 years rent + the value at supermarket organic prices of two years produce + 50%


(Has anyone else had advice on this and who a claim should be made against).


Question: Is anything happening out there officially about this problem?


RHS answer

The manufacturers are very, very disappointed that things have come to this and are putting all their efforts into making sure it does not happen again.  We are going to help them. I would point out that the manufacturers have handled this is a very open, honest and straightforward way and had their instructions on using the weedkiller been followed none of this would have happened.


It would seem that there is a need to raise the standards in the hay, silage and manure trading chain and the manufacturers are going to educate farmers, farm advisors and hay merchants. Since this response see PSD update


Question: Could straw used as a strawberry mulch for instance be contaminated?


RHS answer

Aminopyralid does not currently have approval for use on cereals so is unlikely to find its way into straw used for bedding or under strawberries.


Question: How can we be sure that green waste from our local council is ‘clean’ – can this herbicide be used by parks departments? It seems to me that the only sure way to be certain is to use one’s own compost.


RHS answer

There is one product containing aminopyralid approved for use on amenity grassland but it is not clear how widely this is used. I suspect the number of cases of composted green waste from local councils being contaminated with weedkiller is very small, especially in comparison to manures. You are right that some risk does exists from external sources of organic matter but I feel the benefit of using recycled green waste such as this outweighs the risks. The PSD are going to raise awareness among local authorities to be vigilant of potential green waste contaminants.


Question: If I can't use manure to improve my soil then what can I use?


RHS advice:

Don’t stop using mulch. Organic mulches are essential to improving soil structure and soil moisture. If a reliable source of manure is not available, try using an alternative source of organic matter such as garden compost, leafmould, composted bark or composted green waste from your local council. Although it is possible that composted green waste may sometimes be made from raw materials that contain weedkiller, lawn mowings for example, we have not found this to be a problem. With increasing awareness of the risks associated with weedkiller residues in manure and composted green waste, this problem with hopefully decrease in the future.


RHS web site - Weedkiller Damage no longer available


Has information on symptoms



Use of indicator plants are frequently mentioned and so I asked a few questions about the use of these plants of the RHS:


June - October 2008:

Questions: It is suggested that particularly sensitive indicator plants are planted to test if contamination is still in the soil - how does this work?


RHS answer

Well, if you grow a tomato for example and it is distorted then weedkiller is probably present but if it does not, then the weedkiller might be absent, present at very, very low levels or still attached to hay, silage or straw.


Must admit I am not at all sure how the indicator plant idea will work as if the herbicide residue is only released when the plant material breaks down then the residue could be being released at any time couldn't it?


RHS answer

Exactly, but manure is almost entirely broken down in the first summer after application, hence by next spring it should have been eliminated from the soil by soil microbes.


I am told that after breaking down the residue takes 4 weeks to dissipate so wouldn’t it  depend when the indicator plant was planted and in which area of soil as in our experience the symptoms are not consistent?


RHS answer

You’re a quite right everything depends on good sampling technique and there are no clear protocols for this and rate of breakdown depends on soil moisture, soil temperature, what microbes are present, how big the lumps of dung are and so on and on, leading to problems of interpretation.


Also if the RHS are saying that it would be wise not to eat crops from contaminated soil even if they show no signs of damage what is the advantage of an indicator crop?


RHS answer

If an indicator crop shows no symptoms it must mean that the weedkiller, if present at all, must be at very low concentrations and gardeners may decide to consume their produce, although obviously it is not possible to say that such produce is completely free of weedkiller


Could you explain how we could use an indicator plant to tell us when we would be OK to plant or indeed crop again?


RHS answer

Well, if you take pots of soil next February and plant tomato seedlings in them, and if you do the same with ordinary unmanured soil, and if the treated soil is as free of symptoms as the untreated soil then it should be safe to replant.  But if you are looking for simple assurances of no weedkiller at all, then I am afraid it is not possible to give those assurances.  You have use a smattering of common sense


I am told soya beans are susceptible too and would make a good indicator anything else that grows quickly?


RHS answer

Tomatoes – take sideshoots as cuttings now or raise seedlings at other times.




Input from the USA


Bob from Iowa State University says

I received a call from a person in Maryland reporting problems with tomatoes and potatoes. In terms of enough research being conducted on these products -  I guess in this situation I feel we have an excellent understanding of their behaviour in the environment due to over 50 years of experience with growth regulator herbicides.  Similar problems have been fairly common with products containing picloram (Tordon, Grazon) and clopyralid (Confront, Stinger).


The labels of the products specify clearly that the residues are persistent in the foliage and can be distributed in hay and manure.  I think a couple factors lead to the problems:


  1. pesticide labels are so complex that most users are not going to read all of the warnings and restrictions,
  2. most people have a hard time comprehending the power of these products (that they can persist in hay for several months, be consumed by a cow, and then be present in the manure at toxic concentrations,
  3. the multiple links in the production chain creates a big disconnect.  In Iowa, it wouldn’t be unusual for a hay farmer to call a local co-op saying he has a Canada thistle problem in his pasture and would like the co-op to come out and spray it with something that will clean it up.  The co-op probably would tell him the product name, but the farmer would not know anything about the product.  The farmer could sell the hay to a cattle producer several counties away who would have no idea what the management practices were for producing the hay.  Then the manure could be sold for composting or be spread directly onto fields going into soybean production.  We’ve had problems with manure contaminated with Picloram being spread on soybean fields.


Learning from previous mistakes?


John from Sandwell Allotments Council sent me the following link.


U.S. Composting Council position paper on Clopyralid and composting. Click here to read the full report.


The report is dated August 24 2001 and describes a similar situation to that being experienced by us at the moment. I quote:


"Recent incidents have revealed that the composting industry is vulnerable to contamination from a long-lasting herbicide called clopyralid. In several well-documented cases, compost products from clopyralid-containing feedstocks (including grass clippings, animal bedding, and manures) have damaged non-target crops due to the presence of clopyralid"

The report points to inadequate labelling but goes on to say that the problem doesn't "begin with nor does it end with the label". It further states that:


"Even if clopyralid applicators are provided with an unambiguous, accurate label, there would still be a long chain of communication that must be maintained among applicators, land owners, harvesters of the plant residuals, haulers and the compost facility operators. How will the applicators know how and where the plant residuals will be handled? How will the land owner know what chemical was applied and how the clippings should be managed? How will the compost facility operator know the history of the residuals delivered in the hauler's truck? As a practical matter, it would be impossible to ensure this essential chain of communication, rendering any improvements to the label ineffectual. A solution to the clopyralid-compost issues must provide for effective and continuous communications among all of the parties involved. If such communication cannot be ensured, the USCC strongly questions the appropriateness of continued uncontrolled use of clopyralid".


This is just what we have been saying with respect to our current problem. The actions recommended are too long to repeat here but the report is very readable so click on the link and read it for yourself.


Media coverage


  1. Yorkshire Post coverage click here, click here and click here
  2. Red Orbit published in the US
  3. Observer click here
  4. Article on Allotment and Vegetable Gardening Website
  5. Birmingham Mail click here
  6. August issue of Kitchen Garden magazine has a short article and also a piece in the September issue
  7. Radio Leeds  Breakfast Show interviews
  8. Farmers Weekly article click here published 2007
  9. BBC Southern Counties are featuring the problem at 10.10am next Tuesday
  10. BBC Midlands Today click here
  11. Daily Mail click here
  12. The Westmorland Gazette click here
  13. Wakefield Express click here
  14. Bristol Evening Post
  15. Horse and Hounds click here
  16. Guardian click here
  17. Daventry Express click here
  18. Keighley News click here
  19. Radio 4 iPM Saturday 9 August
  20. Express and Star with follow up on 14 August
  21. BBC Gardeners, World 15 August
  22. The Press and Journal (Scotland)
  23. Farmers' Guardian forum discussed this in length but it has now been made a members only forum
  24. Daily Mail click here
  25. The Politics Show - Yorkshire and Humberside - 16 November 2009
  26. BBC Radio Leeds - Breakfast Show 2 June 2009 with follow-ups later
  27. Cambridge News
  28. Huddersfield Examiner - July 18 2009 Click here
  29. The Express and Star - 7 August 2009 and 20 August 2009
  30. Telegraph - 28 August 2009 click here
  31. Guardian - July 2011 click here


This isn’t a complete list of media coverage as I have removed (December 2011) those links that are no longer available and no doubt there are lots of articles out there that I have not been made aware of. The same applies to the links below.



Forums and Web sites  with threads on the subject and Websites


The more forums we can get talking about the subject the better so we can make sure other gardeners are less likely to have the problems that we have had in the future. If you find any more let me have the links just so we know how we are doing at getting the word out. The intention isn't to take part in all the discussions or even read them but just to get people talking about the problem - raising the profile.


  1. Allotments UK
  2. Kitchen Garden Magazine and here
  3. Allotments for All
  4. Allotments and Vegetable Growing
  5. Gardeners' Corner
  6. My Garden RHS forum
  7. Joe Swift (Gardeners' World) blog
  8. British Farming Forum thread 1 & thread 2 & thread 3. Access is now restricted to members only!
  9. Money Saving Expert
  10. Grab 'N' Grow - Soil Products
  11. Manure Matters - Advice from DOW AgroChemicals 21 May 2009
  12. Problems in the USA click here  10 August 2009
  13. The Guardian Gardening Blog click here
  14. Garden Organic click here



MP’s getting involved


Paul Burstow MP  - Member for Sutton and Cheam asked Parliamentary questions Hansard  - more tabled

Linda McAvan MEP for Yorkshire and Humberside and has worked with REACH REACH is a new European Community Regulation on chemicals and their safe use (EC 1907/2006). It deals with the Registration, Evaluation, Authorisation and Restriction of Chemical substances. The new law entered into force on 1 June 2007.

Tim Brough MP  - Member for East Worthing and Shoreham has asked Parliamentary questions Hansard

Nigel Farage  MEP for South East

Vince Cable MP - Member of Parliament for Twickenham

Tom Watson MP - Member of Parliament for West Bromwich



The MPs mentioned above have been proactive rather than just sending a letter to a minister and forwarding the reply to their constituent. Thanks to them.



Extra reading for those interested:


any of these links point to problems in other countries well before aminopyralid was used in the UK. Some point to problems with clopyralid a similar herbicide.



Thanks to John from Sandwell for pointing me to the following link:

Council Directive 91/414/EEC of 15 July 1991 concerning the placing of plant protection products on the market


Snippets from above EEC Directive

● Member States shall prescribe that plant protection products must be used properly

● Member States shall ensure that a plant protection product is not authorized unless:

                 i(ii) it has no unacceptable effect on plants or plant products;

                   iv it has no harmful effect on human or animal health, directly or indirectly

                       (e.g. through drinking water, food or feed) or on groundwater;


Obviously the snippets above are out of context but are just intended to show that it is the government's responsibility to ensure plant protection products are properly used.


Aminopyralid Milestone review Toxicology dealt with from page 22


Clopyralid by Dow AgroSciences Found in Composted Grass


EMILY GREEN / LA Times dated 27 December 2001


University of Minnesota - advice when disposing of ditch hay (manure)


New York State Department of Environmental Conservation Division of Solid & Hazardous Materials February 2007


Re: Withdrawal of Milestone Herbicide Application (EPA Reg. No. 62719-519) Containing the Active Ingredient Aminopyralid. Chemical Code: 005209 click here


Evaluation of the new active AMINOPYRALID in the product Hotshot Herbicide - Australian Pesticides and Veterinary Medicines Authority,  February 2006, Canberra, Australia No longer available


Aminopyralid Contamination in Farmyard Manure Soil and Land Consultants dated 11 July 2007


Persistent herbicides in compost From BioCycle Journal of Composting & Organics Recycling dated July 2001 no longer available


Tilth Producers quarterly - Clopyralid: The Story of a "Benign Herbicide" dated Spring 2003 no longer available


Position Paper of the US Composting Council

Environmental Policy and Regulatory Affairs Committee

(August 24, 2001) click here


Compost Communicator - The quarterly newsletter of the United States Composting Council


Clopyralid in Compost - Washington State Department updated 2004 no longer available accompanying factsheet dated 2002 (Links no longer available)


Aminopyralid - Dietary Exposure Assessment -  United States Environmental Protection Agency -  dated 21 June 2005


US Environmental Protection Agency dated 5 October 2005

Environmental Fate & Ecological Risk Assessment for the Registration of Aminopyralid


US Officer of Prevention, Pesticides Environmental Protection and Toxic Substance Agency (7501C) dated 10 August 2005


Pesticide Fact Sheet - Aminopyralid


Many of the original links are no longer available but I have left the references.


The lists above show the publicity that was acheved but still many gardeners are unaware unless they have been affected directly'




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Our Plot at Green Lane Allotments Blog  | A Gardener's Weather Diary  | School Vegetable Patch Website


© Our Plot on Green Lane Allotments - Please email me if you wish to use any of this site's content