Don't have to look to Australia to see this. I hear about this several times a year in the U.S. Compost contamination from aminopyralids that make it through the digestive system of bovines is common in the U.S. Responsible providers will do testing to ensure that their compost isn't contaminated by these residues. Getting manure from a random farm that doesn't do testing is a big risk.

I use my hen's poop to add to my own compost piles, never trusted the bagged "stuff" and that includes so called "top soil" and other various bagged garbage being sold out there.

Same problem here -- I only have kitchen scraps and, in early spring, some plant trimmings. A lot of the plant material here is just trashed because it's not compostable (like palm fronds, fibrous succulents, tough woody shrubs).

I trench-compost my kitchen scraps because I never have enough to get a pile going. So off to the compost store we go...

That's why our municipal compost program closed, they didn't have enough staff to ensure it was clear and clean of contaminants. Plus keep it turned. I love the one from the nearby town, but I'm starting to worry and wonder that they are also cutting corners on watching what gets dumped there . . .

Problem is I can't produce enough compost for my

That is the conundrum.

The United States has had a certification program for over 20 years.

Using STA Certified Compost (compostingcouncil.org)

Not clear that STA certification actually tests for persistent herbicides. As of a year or so ago such tests were being strongly recommended, and they were working on approval of such tests. Does anyone know for a fact that STA testing now includes persistent herbicide tests? I think the STA tests have, for a long time, been based just on pH, soluble salts, nutrients, organic matter, particle size, trace elements, and pathogens. Responsible providers will, however, test for herbicides. Those tests are not cheap nor easy, though.

Yeah now that you mention it I don't see them saying anything about herbicide:

Sample_Current_CTDS.pdf (ymaws.com)

Maybe I've never checked or noticed because of previous familiarity with this:

If you depend on commercially available compost, be aware that the US Composting Council has a Seal of Testing Assurance (STA) program. Members in this program must test their products for pathogens, heavy metals, and pesticides on a regular basis. These numbers are available to the public. More information can be found at this website: http://tmecc.org/sta/index.html.

Microsoft Word - B&B #18 - compost problems.doc (wsu.edu)

"Pesticide" is a blanket term that would include any herbicides as well. I feel quite safe using commercially prepared compost available from bulk suppliers as I know they adhere to this program. Bagged compost should should be clearly labeled if it meets STA program standards.

I mulch heavily with compost at least twice a season. There is no way I can generate enough of my own to satisfy my requirements so I rely on purchased bulk compost to fill the bill. Since these requirements (and the banning of any persistent herbicides from any residential usage since early in the 2000's), I do not worry.

I wouldn't be so sure about STA certifying absence of herbicides in compost. At least not yet. If that were the case, there wouldn't be any reason for this ...

https://www.naylornetwork.com/usc-nwl/articles/print.asp?aid=652237

which says that testing procedures for the TMECC will be "ready for evaluation in early 2021".

"The STA Advisory Committee is considering how best to use this upcoming Persistent Herbicide General Indicator lab test method in the STA program."

No date on this article (don't you hate that?) but it is likely to be fairly recent. It was referred to in the Washington Organic Recycling Council (WORC) newsletter in December 2020.

To most any responsible horticulturalist, "pesticide" doesn't mean "herbicide".

Seems to me the only way to be at all safe is to restrict yourself to compost you make on site with onsite organics. But we all know that's never enough particularly when you want to start a new bed or plot. To me the worst thing you can do is go to a large supplier who can never test all the input from multiple sources.

An option is to never use any compost you don't test. Find a small horse barn, check to see if there is old manure. Take a small quantity; with permission. Germinate some seeds let them grow out. Another option is to test mushroom compost. Except that is this case you'll need to buy as much as you need otherwise the compost you buy later won't be the same you tested. Remember in the case of mushroom compost it has already grown two crops of mushrooms; unless they scrapped the load you got. So test it.

Obviously you're going to have to test long before you need the product. Plan ahead. Test it yourself!

As to whether pesticide = herbicide or not (I use it sometimes myself but acknowledge the lack of equivalency), I've seen our local city compost kill established gardens.

It's always best to work with your own where possible, or sources of organics you're familiar with.

One source we like to recommend (it's not compost, but functions as both a feed for lawns and plants, plus rots eventually) is brewer's grains. It can certainly be collected and added to the home compost pile in large amounts if you have a local brewer with the assurance that herbicides are going to be at extremely low and non-fatal levels...

One could say that, hey, self-testing is easy. Just get some bean seeds, plant them in the compost, and wait a month. The problem with that is that if you haven't already bought the compost, who knows whether, when you go back to the pile you took your sample from, if it's really even the same stuff!

It should be said that most persistent herbicides have half-lives less then a few months. So in principle if you buy a pile, and let it sit for a year, it'll be safe.

I take that back. Looking at the literature, "pesticides" can actually include "herbicides". Weird! My apologies. That being the case, however, I don't believe STA tests for pesticides. It does test for "pathogens", which is fecal coliform or salmonella.

"To most any responsible horticulturalist, "pesticide" doesn't mean "herbicide"."

I'm not sure why you would come to this conclusion. The definition is pretty standardized: "Pesticides are substances that are meant to control pests. The term pesticide includes all of the following: herbicides, insecticides (which may include insect growth regulators, termiticides, etc.) nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, antimicrobial, and fungicide. The most common of these are herbicides which account for approximately 80% of all pesticide use."

A pesticide operator's license includes any or all of the above subcategories.....it is not restricted to a single type of pesticide, whatever you think that might be.

Since the common persistent herbicides have been banned from household usage, the risk is primarily from manures or livestock bedding that may contain these products as agricultural usage of these herbicides is allowed. And while these inputs are typically restricted from commercial composting operations, mistakes - unintentional or otherwise - do happen.

One can always do a quick and easy bioassay if you have any doubts.

ETA: Dan, we were posting at the same time so please excuse my detailed clarification :-)

(This has to be one of a gardener's worst nightmares....seeing multiple plants go down for the count and not know exactly why...at a last resort, maybe suspect off property compost but not able to really know for sure :(.)

You were probably typing when I apologized for that comment about pesticide and herbicide.

Quick and easy bioassay for a herbicide? Sorry, but planting seeds and watching to see how the seedlings develop takes weeks.

Bioassays are fast enough, relatively speaking. Beans - one the most common indicator plants - germinate in about a week with proper temps and should show any evidence of herbicide contamination as soon as they produce their first set of true leaves.

Dan's point being that, by that time, one would have already bought the compost or one could not be assured one was working from the same pile or the same part of the greater pile. Even over a week or several days, that's still true.

Testing consistency always presents an issue over any large mass as well, and presents a challenge here, just as it always does when soil testing.

And in a week, one wouldn't be assured--just from sprout--that some herbicides aren't in the soil. If one's a purist, that's a problem. And of course, more subtle effects like stunting of plants won't show until later in the development process (like subtle amounts of the dozen or so growth inhibitors used as herbicides).

And of course, more subtle effects like stunting of plants won't show until later in the development process

And to take it to the 'extreme', if one was applying 'tainted' compost to mature plants eg perennials, it might be even more subtle seeing plants in decline.

Alas, exactly. For the purist, too, a few PPM to a few PPB might not show on a sprout test, but would not be acceptable in the daily diet in one's tomatoes.

There are formulae out there to use Glyphosate to slow growth of lawns and other plants. They're not...recommended, to say the least, but experimenters have tried them and they do work.

I've achieved the effect accidentally by overapplication of kelp in pots and in the garden. It contains growth hormones that, overapplied, start acting like growth inhibitors. Keep going and they'll act like 2,4-D for obvious reasons. :-)

I can deliver a ten minute lecture on why one shouldn't overapply too much alfalfa meal to lawns per year for this very reason as well.

Chemical impact can be a lot more subtle than "does or does not keep plants from sprouting," so I'd say go with the assay where available. But again, one can't be sure that the pile one's assaying will be the one where one gets the compost from.

So I restrict myself to my home source. Since that's limited, I feed heavily and organically in the gardens and on the lawn and let it compost in-place, if slowly. It takes years, but the soils are all gorgeous at this point.

All the extension websites that talk about bioassays for persistent herbicide talk about waiting THREE WEEKS or more to judge effects on seedlings. That's a long time. If you can do it in one week, more power to you, but the experts say you need longer.

A week to 10 days for germination, then another week and half or so to develop at least one set of true leaves.....that's about 3 weeks, so I don't see the discrepancy. And whether or not 3 weeks is a long time in a garden cycle is also up for some discussion. Depends on what you are growing.

Sure, it is always going to be preferable to make and use your own compost, so you can control the ingredients. I'd still be leery of adding any manure or livestock bedding to my compost unless I was certain that livestock was never near any herbicide treated fields or fodder. But if you cannot generate the amount needed at home, it is also possible to seek out certified commercial compost that is tested to be free of any contaminates.

Again, the point being that in three weeks, you won't likely be drawing from the same pile or combination of piles, rendering the test utterly moot, so three weeks might as well be three years.

This also completely ignores any more subtle effects as stated above, where smaller amounts remain that do not stop germination but do inhibit or otherwise impact plant growth, which are unlikely to show in the initial germination cycle.

I won't bother to address the argument as to additions to the pile, it's not germane to the point at hand.

Oh, so now we agree that three weeks is a long time. On a timescale of the lifetime of a compost pile in a purveyor's yard, yes it is. Has nothing to do with what you are growing. Thanks.

But the topic we were discussing is the persistent herbicide safety of STA-certified compost. I agree that STA-certification is very important, considering what COULD be in compost. But I find no evidence that they are certifying that compost is persistent herbicide free. If someone has better info on this, I'd love to hear it. I vaguely recall that someone here was complaining about herbicide-like effects in STA-certified compost. Might have been something to that.

Yes, you can always seek out compost that has been tested for persistent herbicide. The compost my city makes is allegedly tested and guaranteed to be herbicide free. But that isn't STA certification.

My suggestion to find a small horse facility with old manure was so that you know the manure has sat for a good while. That's how it gets well composted. And in that time hopefully any pesticide will have aged out, according to posts above. From many decades of experience I've found that most of the year all manure piles just build up. So if you go there early then most likely there will have never been a visitor to remove any. So your test will still be valuable. Maybe by March there might be some interest.

Because of all the bad mouthing manure has gotten over so many years I find that there is almost no interest. Which is great for me. The pile I've been working for two years has had nothing added to it for all that time. And no one has taken anything from it that I can tell; except me. And the pile is built on the side of a steep hill, so the oldest stuff is always at the bottom of the pile. There is currently 2 horses there so there's fresh manure when I'm ready to fill my hot box later this winter. My pile is maybe 11 miles from downtown Pittsburgh.

The horse manure pile that is closest to me is easier to get out of but they use wood chips for bedding in the stalls. The manure winds up looking like wood chips and one assumes there's some uric acid; but there's no manure. It's right on the road, but when I wander over there there's seldom any evidence of activity. That pile spreads out on near level land, so to find old manure you need to go back toward the barn and dig it into a wheelbarrow and then push it over to your truck. You're leaving a hole that someone could trip into. Not good.

If you check around I feel confident that you can find the ideal pile for you. Start out by googling "Horse boarding Your town State"

Compost piles I've seen in garden centers are used up pretty readily. A new truckload comes in every week or so in mine. Manure piles in small horse facilities might be different. Personally, I have no desire to haul manure around, in any case.

.......morpheuspa gives a suggestion above that I wish to call to your attention. Try to locate a source of beer mash from local brewers to incorporate with your own compost. Takes a bit of footwork visiting brewery owners personally with hat in hand.

It can be spread fresh on gardens, worked lightly into soils (with other amendments if desired) and planted the same week.

It is not easy to find a source of beer mash as the brewers give your local farmers first preference. Persevere! It's usually freely given. Be prepared for the healthiest vegetable gardens you have ever grown.

Or just spread it right on your lawn and gardens fresh and without processing. At 4-1-1 (dry weight; you'll get it wet) it's a fantastic feeding for any plant or your lawn, and composts in situ all by itself with no additional effort.

Catch them on brewing day and you might get up to 120 gallons of used mash. You might also, if you're not careful to keep them in until it's completely dry, accidentally end up with two slightly bloated dogs.

Fresh beer mash is fairly pleasant smelling, but I've heard that if allowed to decompose anaerobically, it gets really vile and icky. Maybe you avoid that by combining with other compostables, but just trying to compost pure mash can be pretty disgusting.

Oh yes spent grains can get very nasty smelling if too much goes into a pile. I once had to take a good size pile entirely apart and use it as mulch (which worked out just fine). I thought for sure the neighbors were going to complain to the city if I didn't act.