Manure has long been the standard way for vegetable gardeners to improve the fertility of their soil. At my local community garden, manure is delivered by the truckload each year and for just a small cost large quantities can be dug into your vegetable plot ready for the next season. This cheap high-nutrient boost is the way many gardeners have been producing vegetables for years but that’s going to have to change. Over the last few months a large number of plots treated with manure have been producing warped and damaged plants and the culprit seems to be a certain weed-killer (herbicide).
Many ‘standard’ pesticides and herbicides have been withdrawn over the last few years: some due to the active ingredient being deemed as unsafe by the EU and others because the manufacturers don’t think it’s worthwhile to go through the more complex approval process that now exists. Although these withdrawals were sanctioned in 2003, EU member states were allowed to apply for a number of ‘essential use’ pesticides to remain in use until June 2007. As a result, it’s only recently that farmers have started switching to newer herbicides and we suddenly have a full-scale problem on our hands.
Gardeners up and down the UK have been reporting that many of their plants have been failing, producing curled-up leaves (see the picture below), distorted and stunted growth, mal-formed vegetables or simply no crop at all. The worst affected plants are potatoes, tomatoes, peas, beans, carrots and some salad crops. Gardeners’ helplines, such as the one run by the RHS, have been inundated with calls and there is a common theme emerging - they’ve all used manure and in many cases this has been contaminated by one particular, relatively new, herbicide.
The culprit seems to be aminopyralid – a hormone-type herbicide which goes under several trade names such as Milestone and Forefront – and is being spread through contaminated manure. It’s produced by a company called Dow AgroSciences and has cost millions of dollars to develop. Aminopyralid is attractive to farmers because it kills a number of persistent weeds in pasture, such as dock, thistles and nettles, and because it persists on plants it requires fewer-than-usual applications. Sources of manure, such as stables, regularly use straw and hay which are usually bought-in from farmers who may be using this herbicide. It’s often difficult to trace who supplied the straw that stables use and people have even reported this problem in manure from cattle who have eaten hay or silage from grass treated with aminopyralid 12 months previously.
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Potatoes affected by aminopyralid. Photo permission of John Harrison.
At this point I should state that I have always been suspicious of using manure and have never put it on my own soil (although I have used a community garden plot that had years of manure applications and could clearly see how much the plants benefited from the nutrient boost!) The problem with using manure in an organic system is that it has very poor traceability: it’s almost impossible to get information about what the animals that produced the manure have been fed or what medication they may have been given.
So what should you do if your crops are affected? Unfortunately no guaranteed solutions exist. The official statement on Dow AgroScience’s site says ‘we suggest damaged produce... should not be consumed’ and recommends that the area is thoroughly rotovated or dug over several times to help the chemicals to degrade, with remaining manure not being used. Other sources suggest that it’s going to take 3 years before crops will be unaffected, though much of this is speculative. A very good round-up of the situation is provided in the excellent articles on www.allotment.org.uk where you will find much active discussion about the issue. Even branded bags of manure sold in garden centres have apparently been contaminated.
Whatever the advise on dealing with this problem, many gardeners are going to feel angry and let-down by the systems that are meant to protect from problems such as these. Most people grow their own food naturally, with many sticking to strict organic principles. In the past this allowed for manure to be part of that process, yet now they find themselves with no usable crop and no certain timescale for the contamination to go away. Dow AgroSciences advise farmers not to sell manure that might contain the weed-killer to gardeners but how do the farmers know what was sprayed on the grass products they bought in? I can only conclude that manure is no longer a safe option for gardeners, due to the poor traceability of sources of animal silage, hay and potentially other problems with animal medication. With large numbers of the public now taking up vegetable growing, the problem is only going to get worse unless the regulations are tightened. Indeed, I believe that nothing short of a ban on the sale of aminopyralid-based products will eradicate this problem.
The only viable solution is to switch to non-animal methods of organic gardening, such as green manures and home-produced compost. For consumers the new Stockfree Organic Certification from the Vegan Organic Network is a guarantee that animal products have not been used in the production of crops and their website contains useful information sheets on improving soil fertility by these means. For those concerned with pesticide residues in gardening, there are excellent tips available on the Pesticide Action Network website in their monthly Gardening Tips.
Please note that due to the potential for legal action by a large corporation such as Dow AgroScience, we have to ask that unsubstantiated comments against the company or its products are not made in our comments section and we reserve the right to edit comments where applicable. However we still welcome comments on this important issue.
