Killer Compost. Please Advise

Licensed sprayers please weigh in.

So basically hay, grass clippings and manure can contain ‘persistent’ herbicides, which, even after composted can kill or distort growth in fruit trees, garden veggies, potted plants, etc. Their half-life is about 18 months. The active ingredients of greatest concern are picloram, clopyralid, and aminopyralid because they can remain active in hay, grass clippings, piles of manure, and compost for an unusually long time.
Apparently the instructions for these say that whatever is sprayed with these ‘persistent’ herbicides is not to be used for composting (for just these reasons).
Anyway this problem is showing up in backyard gardens.

Here in VA

And even to gurus who do gardening shows

So, where does the responsibility lie to inform people about these so that doesn’t happen to us? I called a local supplier of compost and he was totally unaware of the problem. What’s more, his attitude was more like, “Well, we’ve never had that problem. We can’t send every thing we get to the lab. (Let us know if it causes you problems.)”

Quotes from the web (sorry, didn’t always save the link)
“DuPont now has the herbicide aminocyclopyrachlor which has been marketed as Imprelis to the landscape industry–people who need a pesticide license to apply it. However, Scotts is going to be adding it to a product for homeowners– people who don’t have a pesticide applicator license. Watch for it in some of the Scotts Miracle-Gro weed control products in a garden center or big box store near you! They feel they are doing their part to keep them out of your gardens by including on the label instructions to not use what is taken off the fields or landscapes in compost or as mulch. In the real world, however, these things DO end up as compost or mulch.”

Since 2008, we’ve been reporting on the dangers of pyralid herbicides (including Milestone, Forefront and other trade names), which turn grass clippings, manure or hay into killer compost or mulch that can ruin gardens and farmland for years.

After one season of use, Imprelis has been implicated in the injury or death of thousands of trees. Conifers that are growing in or near grassy areas treated with Imprelis, and are showing new growth that is brown and twisted, have been reported in Pennsylvania, Minnesota, Iowa, Delaware , Indiana, Nebraska , Wisconsin, and several other states. Michigan State has published an advisory on What to Do With Imprelis-Affected Trees, and Purdue University in Indiana has set up channels for Imprelis related herbicide complaints, as have Nebraska and Wisconsin.

DuPont never denied Imprelis-treated lawns would create killer compost. Lost in a 19-item bulleted list on Page 7 of the nine-page Imprelis label, we found this language:

“Do not use grass clippings from treated areas for mulching or compost, or allow for collection to composting facilities. Grass clippings must either be left on the treated area, or, if allowed by local yard waste regulations, disposed of in the trash. Applicators must give verbal or written notice to property owner/property managers/residents to not use grass clippings from treated turf for mulch or compost.”

For now, it looks like my only recourse is to get a small sample, plant some beans in it and see if they get distorted growth. I’d like to convince my local guy to at least ASK his suppliers (he wouldn’t give me the info so I could ask), but maybe, if the law says something about this it will motivate him. So that is my question.
Ok so does this label have legal force?


Wow, learning something new


It is a widespread problem. I have made it with kitchen scraps and leaves for at least 8 years. The tomatoes are particularly sensitive.


My soil is so bad adding amendments is the only way I get stuff to grow. Usually I buy processed manure - but from these articles it sounds like nothing is safe.


The label language does have force of law behind it. However unless your compost maker knows where the contaminated grass is coming from, there is nobody to go after if they don’t follow this. The composted may get the contamination from a yard waste recycling facility, or from landscapers, and they might not be able to trace the contamination.

Out here in California the commercial composers do test for this because there have been lawsuits and publicity over it. Try to pressure your composted into testing, because if his compost threatens a farmer’s crop, he will get sued.


Thanks Zea,
An organization called the US Composting Council has a fact sheet for composting facilities which I sent to him. At least he is aware, step 1.

But what I need is an understanding of the force of law those labels have so I can move him off his position of ‘can’t get there from here’…his direct quote…

so many variables and so much time needed . A long education process and a lot of cultural practices to change for some

That’s it. That’s all he wrote. The tragedy is those persistent herbicides not only distort some plants, but they can ruin your soil for YEARS.

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The mechanics of it is that feedlot manure is a problem meat producers will even pay to get rid of. Some people are profiting twice by getting paid to haul the manure, mix it with something brown, turn it with some heavy machinery, and then bag and sell it. You will never get rid of pesticides in compost until you get rid of pesticides in CAFO feed. And that is not going to happen soon. I am completely out of that loop as I only buy grass fed meat locally.

But really, if you have the space, a one year pile of leaves and kitchen scraps will give you plenty. I produce about 400 lbs a year, which I use for transplants, to mix seed for broadcasting, to make sprouts in winter, or to cover a row of seed. I don’t use it for fertilization because after a few applications (my last one was around 2011) you only need some nitrogen and some cover crops and mulch.


I think I had this problem with some city landfill compost I added to my garden and grapes when I was created several years ago. Deformed leaves and death of some plants, however others appear to do fine with it… Now I make my own compost using yard waste and rabbit manure from my 3 pet rabbits. So far its going fine, but I guess if the rabbit feed ever ends up contaminated, it will cause me problems also… I buy hay from a local guy and also pellets from the farm store. :S


I’ve always been hesitant to use city compost after reading about this stuff years ago on the conifer forum on the other site. I’m to the point now where i make enough of my own compost to be good. Using woodchips should be safe?


I do get wood chips from the dump and have never had an issue with them. I always look for nice fresh ones, hardwood if I can find, but their arent a lot of hardwoods that grow here, cottonwood is the most common. Cant beat a pickup box full of woodchips for less than $5…


woodchips, leaves, shrub trimmings and kitchen scraps are safe. Grass clippings, straw and manure are not unless they are your own or otherwise know the source.


What I was hoping to get is spent mushroom compost but I can’t get his suppliers names to check with them.
Does anyone know how to find local sources for spent mushroom compost? I’ve tried googling every way I know how.

We live in the eastern rain forest and potential hurricane driveby site, so there are LOTS of woodchips to be had for free. Esp during hurricane season which is coming up. Sometimes people see them coming and cut down trees to prevent house damage. I guess I need to stock up again. Somehow I let myself get slam out.

Does anyone know the best ‘test’ plants to use to check of compost is contaminated? Im guessing the best practice for gardeners is to get compost, test compost, use compost, in that order… Preferably getting large quantities at a time so if you know its good, it will last a while.

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From what I’ve posted and read, beans are one of the vulnerable plants. Actually I’m testing some today in 1/2 my compost, 1/2 mushroom compost from a local facility.[quote=“TheDerek, post:13, topic:12281”]
get compost, test compost, use compost, in that order.

I was thinking of going and getting a sample beforehand, so more like test compost, get compost, use compost.

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Grass fed livestock manure is at much greater risk of the persistent herbicides mentioned than CAFO livestock feeding operations. Of course it’s possible (and has happened that CAFO feed has persistent herbicides, but it’s probably more likely common in grass fed livestock. None of the examples JustAnne mentioned came from CAFO feeding operations (although it wouldn’t surprise me if someone could produce an example from somewhere, but of course an example doesn’t make a rule).

Picloram is not even labeled for corn, but is used extensively on pastures, so should rarely (if ever) be found in CAFO livestock feed. Aminopyralid can be used on fallow land planted to corn, but has an extensive plant back interval for corn.

Clopyralid is labeled for post emergent spray on corn, but the cost/acre is quite expensive nowadays. I doubt it’s used much on corn today, as there are much cheaper products, with better overall action and less persistence, for corn. I personally used Dual Magnum and Callisto as a combo mix for post emergence on my sweet corn this year, and got excellent control at a cheaper price than the Clopyralid (Stinger) I use in the row middles of the peach orchard to control clover.

Again, I won’t say that at some point someone hasn’t found feed somewhere contaminated with these persistent chemicals, but they are primarily used on rangeland, pasture, golf courses, and (regarding Clopyralid) lawns.

Regarding CAFO manure disposal, I’ve been involved w/ CAFOs for a significant part of my work life. At one point I was a Field Manager for a commodities company which had over 100 contract CAFO hog producers. I’m not aware of a single one who paid to have their manure removed. They considered it valuable. Many of these producers also had contract CAFO poultry houses with a different company. We would also talk about their poultry houses. Likewise, I was never aware of any poultry grower who paid to have their manure removed, although they did sometimes sell their manure. Most of the time manure simply stayed on the farm.

I also used to own a CAFO, which had a two acre manure lagoon. We never paid to have any manure removed, but used it on our own fields. The person I sold it to has since told me he occasionally sells manure to another farmer, who uses it on his fields.

I would be interested to know any statistics of CAFO manure which actually ends up as compost, if anyone can obtain them.



I think it is generally recommended to use crop you actually intend to plant in the compost, as a bioassay plant, since it would be hard to find any one plant the most herbicide sensitive to all herbicides.

That said, perhaps the red beans JustAnne mentioned are some of the most sensitive to the persistent herbicides mentioned in the articles, I don’t know.

It’s been my experience tomatoes are very sensitive to most broad leaf herbicides. I’ve even killed tomatoes by using walnut sawdust as a mulch (i.e. juglone in the wood).


There are tons of mushroom houses around here, I’m no expert, but the reason I heard is that the nearby horse industry mostly prefers to use straw for bedding instead of sawdust. I don’t think they actually use horse manure, but probably do use some spoiled hay along with the spent bedding.

I’ve only bought a few bags in the past and didn’t like it, too dense. The shiitake and oyster blocks would probably make a much nicer product but would take much longer than the button and portobello compost.


I would be concerned on a regional basis, but I’ve used compost from a town composting project that gave composted leaves and lawn clippings away for free. Big town- Mt Kisco, with residents willing to pay for pristine lawns but happy to take free compost. If such a problem was wide spread, word would get to cooperative extension and from their likely spread widely. Here in NY, I’d be comfortable to use such municipal compost if the county cooperative extension wasn’t aware of any issues with it.

None of Anne’s reports can really give any ballpark of how frequently this is a problem. I’m in the business and a lot of towns do compost their leaves and lawn clippings these days, and I’ve not heard of any issues like this at all. Anne has peaked my curiosity, though, and I will bring it up with my hort agent next time I see her- it is a topic she would be very interested in. .


In my garden, no tellin’ what will be planted in any spot over the next 3 years, say, whilst the herbicide is still active (the big problem is that these are persistent). So for my purposes a test plant that is very sensitive, shows the results early in its growth, and with unmistakable indicators would be best for me. I just don’t want poisons in my garden actually, no matter what I crop esp the long lasting ones. From what I’ve read, beans have been recommended so we will see.


Do you have mushroom growers in your area? When I was in PA i would just go shovel my own for free at the mushroom growers facilities as they welcomed locals doing so. I definitely miss having that supply! This was the place I mostly frequented: