In 2008, 2009, 20010, 2011, 2012, and 2013 there have been many reports from allotments all over the UK of manure having been contaminated by residues of a herbicide called “aminopyralid”. This has caused major damage or even failure, to crops of potatoes, tomatoes, peas, beans, carrots, lettuce and similar crops,where the manure has been used as a fertiliser. How did “aminopyralid” get into the manure?
Apparently, this happens where farmers have sprayed their grass fields with this hormonal weed killer to kill broad leaved weeds in their crops of grass. This grass is later cut, made into silage or hay for feeding to animals such as cattle and horses. Residues of this persistent weed killer pass through cattle and horses unchanged and end up in their manure.
Only when the contaminated manure has been dug into the soil and exposed to the soil bacteria, will the weed killer start to be broken down. As the plant material in the manure breaks down it releases the aminopyralid, which is likely to be at its highest level in the soil about 3 weeks after digging the manure into the soil. However, soil bacteria then continue to break down the manure so that susceptible plants may even start to recover and grow again where the aminopyralid contamination has been minimal. However, any crop may be only 25% of the normal expected yield depending on the degree of contamination with aminopyralid.
On present indications, the complete breakdown of the aminopyralid contaminated manure already dug in to the ground, is likely to take at least a growing season and often 2 or 3 seasons. It would be prudent not to grow any of the sensitive crops, in ground previously contaminated with aminopyralid for at least 3 years.
Tests done by the Canadian Regulatory Authorities suggest that in clay loam soils, it can take up to two years for the aminopyralid to be released. Recent experience in the UK with potatoes still show the effects even after 3 seasons with poor and stunted growth.
As the aminopyralid is released into the soil, it can be carried for several metres in the groundwater and affect sensitive crops where no manure has been spread.
If the manure has been stored in manure heaps, the breakdown of the contaminated manure will not start until it has been added to the soil. If the contaminated manure is left in heaps, breakdown of the aminopyralid contaminated manure could take 5 years or more to be complete. In this case where possible, you may wish to return the manure to the supplier.
The only way to prevent this disaster happening to you, is to make searching enquiries of the manure supplier as to the provenance, to ensure that the animals have not been fed on grass treated with this weed killer. Many suppliers of manure, such as stables, will be unable to confirm that their animals have not been fed with contaminated feed. If you cannot get absolute confirmation that the manure has not been contaminated with aminopyralid, it would be better to avoid that source of manure.
After checking the provenance as above and you do buy manure, make sure that you test it for aminopyralid contamination, using the test detailed below, before you add it to your growing beds. Keep it in a heap until the test proves that it is safe.
Unbelievably, aminopyralid has now been re-licensed for use on farms in the UK, although with some restrictions which will be difficult to enforce. It is highly likely that contaminated manure will be available for several years to come. There must be thousands of tons of contaminated manure already stockpiled on farms and stables and this will cause continuing problems for plotters and gardeners. Aminopyralid is made by Dow Agroscience, and is present in several products including, Banish, Forefront, Halcyon, Pharoah, Pro-banish, Runway(now Mileway).
Stop press !! Dow chemicals has offered to collect manure contaminated with aminopyralid if you contact them before the 16th of October 2009. For details, see my blog page. If you missed this deadline, they may still collect.
Tests for aminopyralid contamination of manure. Professional testing for aminopyralid contamination is expensive, some £200.
The following amateur test for aminopyralid contamination has been suggested, but does require a few weeks for the results to be visible. Not only does it take time for the broad beans to grow, but it also takes several weeks for the soil bacteria to start to break down the manure and release the aminopyralid that damages the test broad beans. The test will only indicate if there is a high level of aminopyralid present. It will not pick up levels of aminopyralid too low to distort the foliage, but still great enough to reduce the normal crop.
1. Take small samples from various parts of your manure heap, mix them together in a pot and then combine them with the same quantity of your soil.
2. Put the mixture into a 15 cm pot or similar and plant up with broad beans seeds. This quick growing broad leaved crop is particularly and obviously susceptible to aminopyralid contamination.
3. Plant up another 15 cm pot of your garden soil with broad beans at the same time as a control. Do not stand the pots on the same tray, otherwise the aminopyralid will contaminate the control pot.
4. Place the pots in a sheltered position, such as a cloche, cold frame or greenhouse to get quick growth of the beans, especially if testing in the Autumn or Spring.
5. Compare the leaves and growth of the test pot and the control pot. If the leaves of the growing seedlings become distorted and unnatural, as shown in the photo on the right, then assume aminopyralid contamination, and do not add the manure to your soil.
The photos show tests carried out on both peas and broad beans. It is easier to see the effects of contamination on the broad beans.
There is also the possibility that another broad leaved herbicide called clopyralid, might have been used on garden lawns. Any grass clippings used as mulch or compost will cause the same sort of damage to edible plants. Make sure that you read the label very, very carefully before you apply any chemicals to your lawn!
Do not use any of the grass clippings, treated with clopyralid, for composting or mulching.
Do not put the grass clippings, treated with clopyralid, out for collection for recycling green waste by the Council, as this can lead to contamination of commercial products, such as “peat free” growbags and liquid organic fertilizers. There have already been recalls of such products because of clopyralid contamination.
Visual Conformation of aminopyralid contamination of manure.
Once seen, this condition is easy to spot as the growing tips of the affected plants become distorted with upturned, spoon shaped leaves and when there is severe aminopyralid contamination, “fern like” leaves. The severity of the condition increases with the amount of contaminated manure applied to the crop. The crops most likely to be affected are potatoes, tomatoes, peas, beans, carrots, peppers, lettuce and similar crops.
According to Dow, very heavy contamination of soil with aminopyralid may affect leeks, onions, shallots and garlic.
According to Dow, Cane fruits, such as raspberries, gooseberries, blackcurrants, redcurrants and white currants do show some sensitivity to residues of aminopyralid, but not to the same degree as potatoes, tomatoes, carrots and legumes.
After the top-dressed aminopyralid contaminated manure was removed, normal re-growth of the raspberry canes resumed after some 2 months. See photo to the right and note the new normal growth at the top of the photo, with the old contorted growth at my fingertips.
From observations, young trees may be severely damaged or even killed by aminopyralid contaminated manure.
According to Dow, plant species which exhibit less sensitivity to aminopyralid include:
Grasses, Sweet corn, Brassicae (e.g. broccoli, cabbage, cauliflower), established top fruit trees (e.g. apples, pears)
Suggested procedure following damage from Aminopyralid contaminated manure.
If you have already dug in the aminopyralid contaminated manure, there is not much you can do to alleviate the damage. Where the contamination is severe, it is unlikely that the crop will recover. At the end of the season, thoroughly dig over the contaminated ground. Do not add the plant remains to your compost heap as they will still contain aminopyralid. Instead, dig them into the ground. Do not plant any sensitive crops in the same ground for at least a year.
If you have top-dressed the plants with aminopyralid contaminated manure, such as is sometimes done with potatoes, fruit bushes and trees, you may be able to lessen the damage by scraping off the contaminated manure as quickly as possible. Do not plant any sensitive crops in the same ground for at least a year.
If you still have a heap of contaminated manure left over, try to get it taken off the site if possible. Failing that option, leave it to decompose for several years in an out of the way spot. Before using it, carry out the “broad bean” test as detailed above.
Alternatively, dig it into a bed that is already contaminated and that you can leave fallow until the next year. This will allow the soil bacteria to break down the aminopyralid contamination. Do not plant any sensitive crops in that bed for the next year.
If you have suffered damage from aminopyralid contaminated bagged manure, (quite a few reports of this happening), return it to the supplier and demand a refund.
Useful information on aminopyralid contamination of manure.
For a full history and locations of known manure contamination, visit the Green Lane Allotment site at http://ossettweather.com/glallotments.co.uk/acmanure.html
If you know of other contamination, add the information to their site.
The RHS has general information on weed killers in manure here http://apps.rhs.org.uk/advicesearch/profile.aspx?PID=477
The Health and Safety executive have confirmed that vegetables that have been grown in ground contaminated with aminopyralid, are safe to eat.
Many growers, to be on the safe side, may choose to avoid eating vegetables grown in ground contaminated with aminopyralid.
Dow, the maker of aminopyralid, has set up an information page at http://www.dowagro.com/uk/grass_bites/faq/allotment.htm
If you have been affected by contaminated manure, you should e-mail Dow advising them of your problems using this address email@example.com.
This is to ensure that they and the Authorities are aware of the extent of the problem. Make sure that you carry out the preventative measures mentioned earlier.
The advisory committee on pesticides.
You can see the minutes of the committee here http://www.pesticides.gov.uk/acp.asp?id=2691
From the above page, you can use the “contacting us” button to e-mail the advisory committee to make representations against the licensing of aminopyralid.
There are links on the above page to contact the Scottish Executive or the National Assembly for Wales.
It might be useful to make representations to your MP concerning the continuing problems of the use of aminopyralid. Last year, this proved very effective is securing the temporary suspension of the use of aminopyralid after questions were asked in parliament.
Contacting your Elected Representatives.
This is now easy if you use the following site www.writetothem.com
Type in your postcode and you will be able to select the relevant Councillors, MP, MEPs, MSPs, or Northern Ireland, Welsh and London AMs that you wish to write to.
To help you write to your elected representative about Aminopyralid in contaminated manure, feel free to use and adapt information contained on this page, within your reply.