Herbicide Contamination Of “Organic” Manure.

joker-card-01.jpgHow To Screw Organic Farmers

In a recent issue of our local paper, there was a tragic story about how several organic farmers in the region had unknowingly purchased manure which turned out to be contaminated with a powerful herbicide. Consequently, they lost most of their crops. And they certainly lost their organic seal of approval.

How did this happen? And how common is it for organic growers to be screwed in this way?

This story led me to investigate instances of herbicide contamination in so-called “organic” manure.

It turns out that instances of this problem have been reported for several years. Cases were well documented in England in 2008 and 2009. ( Map of contaminated manure UK 2008/2009 ) Indeed, the herbicide in question was banned in the UK, at least, for time. (UK ban petition) It was reinstated in April, 2010.

Here’s the story.

As described in a previous posting, many herbicides work by interfering with the plant hormone auxin. These so-called auxinic herbicides have been around for long time. So long that some plant species targeted by these herbicides have developed resistance to them.

Chemical companies such as Dow Chemical have overcome this resistance by making chemical modifications to these herbicides in order to create new versions. An example of this is the herbicide aminopyralid.

This herbicide was introduced several years ago and is proven to be a problem because of its resistance to biological breakdown. It persists in hay, manure, compost, and grass clippings (also, see refs below).

From the makers of this product: DOW Agrosciences UK and DOW Agrosciences USA

Does your manure contain herbicides?

Bioassay for herbicides in manure – Mother Earth News

And, finally, a personal story – Persephone Farms.


1. Aminopyralid Residues in Compost and other Organic Amendments – Whatcom County Extension

2. Persistent Pesticide As Organics Recycling Foe

3. Davis, J., S.E. Johnson, and K. Jennings (2010) “Herbicide Carryover in Hay, Manure, Compost, and Grass Clippings: Caution to Hay Producers, Livestock Owners, Farmers, and Home Gardeners”, North Carolina Cooperative Extension. (PDF)

4. Aminopyralid Family of Herbicides, Dow AgroSciences (2010) (PDF)

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One Comment

  1. Thanks for sharing all of your experiences!

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