Three years ago, amateur gardeners and smallholders who chose to use manure to improve the fertility of their soil were troubled by a strange disease that affected their plants. It turned out to be damage caused by aminopyralid contamination. Aminopyralid is a herbicide used to kill weeds in pasture land. Unfortunately it can survive passage through an animal’s digestive system and be present in their manure in a form that is still damaging to plants.

It was originally thought that more comprehensive composting of the manure would solve the problem, and that affected gardeners would be fine the following year – which turned out not to be the case. There was a short-term ban on aminopyralid, but it was licensed for use again providing that the farmers who used it followed special guidelines – the manure produced by animals grazing on treated fields was not to leave the farm.

Unfortunately, it seems that this hasn’t solved the problem for gardeners. According to George Monbiot in the Guardian yesterday, contaminated manure is still finding its way into gardens and causing problems. Although in theory cases can and should be investigated, it is proving difficult to track the contaminated manure back to its supplier.

And many gardeners may not recognise the damage this chemical causes in plants, or suspect contamination if they garden organically. The Guardian article has some photos of affected crops, and links to more from John Mason. Green Lane Allotments are still collecting information from gardeners on this topic, and offering advice on their blog.