Herbicide Contamination In Manure and Compost
Y'all know that I always strongly encourage gardeners to add organic material to their soil to improve its' tilth, fertility, drainage and ability to hold moisture. I encourage mulching as well. Two materials that we use to improve our gardens are compost and animal manure. This summer, thousands of gardeners in Great Britain encountered severe problems that apparently resulted from the use of cow or horse manure and/or compost. The compost and manure are believed to have been contaminated with herbicide residue. The specific herbicide in question is produced and marketed by DowAgroscience and is known as aminopyralid. When I first read about this contamination and saw the "pyralid" in the product name, my mind wandered back to the early 2000s and a similar situation that arose with picloram and clopyralid.
SUMMER OF 2008 IN GREAT BRITAIN: Gardeners began to notice distorted growth on many plants. The problem seemed most severe on many broad-leaved vegetables, but also affected some ornamental plants like roses. Tomatoes, potatoes, lettuce, carrots, beans and peas seemed most susceptible to the herbicide damage. The squash family seemed least affected. (I don't know why.) In most cases, the damage showed up as cupped leaves, distorted fern-like foliage, pale color, disorted growth with prominent veining, and stunted growth that did not produce crops.
The common thread was that the gardeners were raising crops in soil that somehow had become contaminated with aminopyralid. In some cases, they had purchased manure, stable bedding (manure plus urine-soaked animal bedding) or hay/straw from local farmers. In other cases, they had purchased commercially-bagged manure. In at least one case, the product was ORGANIC manure purchased in bags. Some gardeners found that the supposedly sterile seed-starting mixes they used were contaminated, so their plants were affected from the very start.
After a couple of months of intense scrutiny and reporting on the situation by British gardening/agriculture interests, including discussion on gardening blogs and forums, the sale of aminopyralid was suspended. I believe I read somewhere that it was the UK branch of Dow Agroscience that made the decision to suspend sale and use of the product with the permission/support of the government. However, the product was not recalled and people who already purchased the product still retain it and, presumably, have it stored.
WHAT DOES THIS MEAN FOR US? Well, first of all, aminopyralid IS sold and used in the USA, so we could see the same chain of events occur here that occured in Great Britain this summer. Therefore, each of us must be careful about the source of ANY manure, composted manure, manure/stable bedding, hay, straw or compost that we use in our landscapes in any way. Unless you are using only products raised on your own property, with no outside inputs, you have no way of knowing if aminopyralid has been used on anything that went into manure, compost, hay, straw, etc. So, be sure of your sources.
I have lots of wonderful farm and ranch neighbors who often give me hay, straw and manure, but I am careful to find out from them if it might be contaminated with a herbicide residue. If there is any doubt in my mind, I don't use the hay, straw or manure. I also only purchase bagged manure or compost from reliable sources.
Some of you have cattle and horses and use their manure in your own gardening operations. Remember that, if you purchase hay or feed for them that has been contaminated by this herbicide, you could inadvertently contaminate your own garden if you use that manure or stable bedding.
HOW LONG DOES IT LAST? I am not sure that anyone is positive. From what I read, gardeners in Great Britain were told to harvest this year's crops (if their gardens produced anything to harvest), remove the residue, leave the garden plots fallow next year (2009) and then their garden soil probably would be safe to use the following year (2010). I suppose we won't really know, though, until someone tries it. From what I remember from the similar picloram/clopyralid contamination problem in the early 2000s, though, it seems like the contaminated soil wasn't usable, in some cases, for 3 or 4 years or more. I think that Dow's own data shows a chemical half-life of aminopyralid of 533 days. No one is saying how long it is known to persist in the soil.
IF YOU'VE USED A PRODUCT CONTAINING AMINOPYRALID: If you know that you have used a herbicide containing aminopyralid and you're wondering how long your soil, hay, straw, compost or manure may retain traces of this herbicide, you probably should contact Dow directly for advice on how to proceed. Sometimes, when you have herbicide residue contamination in your soil, you can reduce its' effect by adding lots and lots and lots more uncontaminated organic material to the soil.
PICLORAM AND CLOPYRALID: In the early 2000s, these two herbicides showed up in home gardens and some commercial gardening operations in several ways. In Washington state, it was determined that grass clippings treated with these herbicides were collected curbside by some cities that ran their own composting facitilities and then sold/gave the resulting compost to their citizens. I believe something similar happened on a large-scale in Pennsylvania as well.
I believe some bagged compost or manure that people purchased in other places may have had the same issues, based on anecdotal evidence.
In numerous other cases from various parts of the country, landowners used the products on their own property and then let cattle graze on pasture land or range land treated with picloram and clopyralid. Because neither of these herbicides metabolizes in the animal's body, the herbicide residues were excreted in the animal's urine, thereby contaminating manure, straw or hay bedding, and even the ground. IF that manure or staw/hay bedding found its way into compost or was directly applied to gardens, the herbicide was then introduced to the garden where it damaged and killed plants.
In many cases, well-meaning farmers and ranchers gave straw, hay, manure and manure/bedding mixes to family members, friends or neighbors for use in their compost piles or gardens. Even after composting, the herbicide residue remained and damaged crops. A lot of gardeners found NOTHING would grow in their contaminated soil.
Finally, please understand that I am not blaming the manufacturer of aminopyralid OR picloram OR clopyralid (or similar compounds) for what happened later with herbicide residues from their products, either in the recent cases or in the cases from the early 2000s. I am confident that they did not foresee having residues of their product end up in compost or manure and affecting gardeners. I do somewhat believe the EPA to be at fault here.....if it is their "job" or "mission" to make sure that a product is safe, they need to do a better job.
I think that there are plenty of times when people buy and apply products without reading all the precautions and warnings on the labels. That is one way that chemical residues end up in places they shouldn't--because at some step in the process, somebody may have used a product in a manner that did not comply with label directions, warnings and precautions.
So, ultimately, each one of us is responsible for what we use on our plants and our soil. I just wanted to make everyone aware that aminopyralid is out there, and this problem has occurred in Great Britain. Has it happened here? Probably. I distinctly remember reading someone's posts on one forum or another this summer where they mentioned that, in the last couple of years, they'd lost their veggie garden due to herbicide contamination, although I don't think they specifically mentioned WHICH herbicide that they thought was responsible.
If you want to read more about the problems gardeners in Great Britain encountered this year with this herbicide, you can Google "aminopyralid" OR go to the bottom of the Wiki page and visit some of the External Links listed there. Wikipedia's brief entry on aminopyralid is linked below. Finally, the current issue (October/November 2008) of the magazine MOTHER EARTH NEWS has a one page article on this topic, written by two very well-known organic gardening writers, Cheryl Long and Barbara Pleasant. Their article contains a boxed quote from Shirley Murray that perfectly describes the whole issue in one very memorable sentence. I hope you'll find the article and read it.
Happy (and Safe) Gardening,
Here is a link that might be useful: Wiki entry on Aminopyralid