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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.

Why not browse the rest of my site too? - It's not ONLY about manure!

If you have a pile of contaminated manure contact the Manure Matters website as DOW will arrange to have it removed.

Manure Matters website
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

Latest information on above

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.

Linda is very happy for you to publish her letter on your website. If you would like a copy of the final agreement on the directive, you should be able to access the document on this website

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 Click hereto visit

DOW's website announcement of temporary withdrawal:

11 July 2008
Immediate Suspension of UK Sales and Use of Herbicides Containing Aminopyralid.

Consistent with its long-standing commitments to product stewardship, and in cooperation with United Kingdom regulators, Dow AgroSciences has asked the Pesticide Safety Directorate (PSD) for a temporary suspension of sales and use of herbicides containing aminopyralid. The suspension shall remain in place until assurances can be given that the product and subsequent treated forage and resultant animal wastes will be handled correctly.
The move comes after reports that manures containing traces of the herbicide had allegedly led to damage of sensitive vegetable crops. Such use of manures from treated forage is in contradiction of warnings on the product label that were part of the conditions of use that form the basis of the approval for the product.
"We are very disappointed at having to take this step because for livestock farmers, the  product  has offered real benefits in terms of the most effective control of injurious and pervasive grassland weeds that reduce production and even threaten livestock health," said Colin Bowers, Grassland Manager. "These benefits depend on users following the approved directions for use. Where conditions of use are not reliably being met, it is appropriate for us to voluntarily suspend use while there are further investigations and a revised stewardship programme developed."
"Aminopyralid has been widely used elsewhere in the world for the past two years," said Mr. Bowers.  "This issue appears to be prominent in the U.K. due to the established links between the farming and gardening communities."
PSD has previously determined that using manure containing aminopyralid residues poses no concern for human health. The product is, however, highly effective against certain plant species, which is why label directions specifically warn users not to use waste from animals fed, or grazed on treated grass, for composting or mulching sensitive plants such as peas, beans, carrots, lettuce, potatoes and tomatoes.
Aminopyralid is highly valued by livestock farmers for providing very effective control of invasive and injurious weeds. Managing such weeds has welfare benefits for livestock, as well as allowing farmers to farm productively.  

Frequently Asked Questions:

June - October 2008
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.

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

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.

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.

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).

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

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.

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.

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 click here

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:
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.

For those interested Bioassay Tests for Herbicide Residues in Compost -  click here

Input from the USA

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

Yorkshire Post click here and follow up article click here and letter published click here and scroll to second letter

Red Orbit published in the US

Observer click here

Article on Allotment and Vegetable Gardening Website click here

Birmingham Mail click here

August issue of Kitchen Garden magazine has a short article and also a piece in the September issue

Radio Leeds  Breakfast Show interviews

Farmers Weekly article click here published 2007

BBC Southern Counties are featuring the problem at 10.10am next Tuesday

BBC Midlands Today click here

Daily Mail click here

The Westmorland Gazette click here

Wakefield Express click here

Bristol Evening Post click here

Horse and Hounds click here

Guardian click here

Daventry Express click here

Keighley News click here

Radio 4 iPM Saturday 9 August

Express and Star click here follow up on 14 August

BBC Gardeners, World 15 August

The Press and Journal (Scotland) click here

Farmers' Guardian forum discussed this in length but it has now been made a members only forum

Daily Mail click here

The Politics Show - Yorkshire and Humberside - 16 November 2009

BBC Radio Leeds - Breakfast Show 2 June 2009 with follow-ups later

Cambridge News click here

Huddersfield Examiner - July 18 2009 Click here

The Express and Star - 7 August 2009 click here and 20 August 2009 click here

Telegraph - 28 August 2009 click here

Guardian - July 2011 click here

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.

Allotments UK

Kitchen Garden Magazine and here

Allotments for All

Allotments and Vegetable Growing

Gardeners' Corner

My Garden RHS forum

Joe Swift (Gardeners' World) blog

British Farming Forum thread 1 & thread 2 & thread 3. Access is now restricted to members only!

Money Saving Expert

Grab 'N' Grow - Soil Products

Manure Matters - Advice from DOW AgroChemicals 21 May 2009

Problems in the USA click here  10 August 2009 

The Guardian Gardening Blog click here

Garden Organic click here

MP’s getting involved

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

Linda McAvan MEP click here 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 click here - Member for East Worthing and Shoreham has asked Parliamentary questions Hansard

Nigel Farage MEP click here MEP for South East

Vince Cable MP - Member of Parliament for Twickenham click here

Tom Watson MP - Member of Parliament for West Bromwich click here and here

If you wish to involve your MP or MEP and don't know how to contact them then try using this link - Write to Them

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:

Many 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.

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 click here Toxicology dealt with from page 22

Clopyralid by Dow AgroSciences Found in Composted Grass  

EMILY GREEN / LA Times dated 27 December 2001 click here

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

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 click here 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 click here

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 - click here 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


I keep finding typos in all this - so sorry if you find some too - I am trying to correct as many as I can and update as often as possible - thanks to everyone supplying information for us to share! As this information has been transferred from another website I may have missed some of the links - please email me if any links are inactive.

By the way why not browse some other pages now you have found us?

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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.
Aminopyralid Contamination of Manure
Manure - Victims of Contaminated Maure in 2008