Pesticide Residues in Cotton Burr Compost

toxcrusadr(Zone 6a - MO)April 14, 2014

This question has come up several times so I thought it would be a good idea to research it and see what we can find. Questions:

1) What herbicides are used on cotton?
2) Are they potentially a problem for your garden when using cotton burr compost?

There might be other questions and I'm open to suggestions. I assume the important question is plant damage from persistent herbicides.

First things first. I did a quick search for "cotton herbicides" and mostly found pages from manufacturers wanting to sell their products. I did find one paper listing some cotton herbicide regimens:

Products listed in this paper:
Glyphosate (Roundup)
MSMA (sodium methanearsonate)

If anyone has direct knowledge or references for more herbicides currently in use, please post. I will add to the list by editing this post. Then we can talk about persistence. Maybe TXEB will show up to give us a hand.

I would like to answer this definitively because 1) there seems to be a general opinion that a lot of pesticides are used on cotton, and 2) cotton burr compost can be excellent compost in terms of organic matter and nutrient content.

This post was edited by toxcrusadr on Tue, Apr 15, 14 at 11:10

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All chemicals used on cotton now must be bio-degradable within two weeks of application.

    Bookmark   April 14, 2014 at 2:10PM
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toxcrusadr(Zone 6a - MO)

That's great news, do you know whose regulation that is? EPA (FIFRA), USDA...? It would be great to have a link.

This project may be quite a bit simpler than I expected. :-]

    Bookmark   April 14, 2014 at 3:46PM
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This is from a company selling the stuff, but might be worth a read as it verifies what lazygardens said. I'm a skeptic by nature.....

    Bookmark   April 14, 2014 at 3:54PM
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toxcrusadr(Zone 6a - MO)

sjerin, did you forget a link?

I posed the question to EPA through their website, I'll post what I get back.

    Bookmark   April 14, 2014 at 4:08PM
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Some of those are used pre-planting...especially paraquat, which is used in small amounts and generally by brush/wick applications (it's not good stuff to come in contact with). Diuron, Fomesafen, and Pendimethalin are other ones generally used pre-planting.

They're not going to be found in boll-formed residues in any concentration worth worrying about.

Also, Valor = Flumioxazin. This is "weird" herbicide in it's mode of action. It's applied shortly before or shortly after germination/emergence of the crop. The crop breaks through the surface of the soil and grows just fine, but after a moisture event (which means application timing is important) it forms a barrier on top of the soil which keeps weed seeds that it's labeled to prevent from emerging. The weed seeds are perfectly viable and if the land is tilled or the barrier is otherwise broken those seeds will begin to grow as normal. It's a neat chemical weed protection.

    Bookmark   April 14, 2014 at 5:59PM
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    Bookmark   April 14, 2014 at 8:20PM
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Tox, you start by talking about pesticides, insect killers, on cotton and then list several herbicides, plant killers. Different things, even though a lot of herbicides on used on "conventional" cotton fields as well.
Since cotton is not an edible crop why would anyone think they must be biodegradable within two weeks of application? There are now systemic insecticides being used on cotton and some research indicates those are throughout the plant, in every part.

Here is a link that might be useful: pesticides used on cotton

    Bookmark   April 15, 2014 at 6:47AM
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toxcrusadr(Zone 6a - MO)

nc-crn: excellent info, thanks!

sjerin: Thanks for the link. That's the page for the brand of CBC that I get locally here in central MO. I never thought of looking them up. I see that they say "The USDA and EPA now require that all chemicals used on cotton be biodegradable within a two week period." But they don't give a link so we're still on the hunt for those regs.

kimmsr: I generally use the term pesticides to refer to all herbicides, fungicides and insecticides, which may not be quite correct (or the same as others). In any case the page you linked mentions various problems related to their use on cotton, but unless I missed it there was no list of chemicals in current use. I'm happy to include anything in the evaluation that is actually being used on cotton, so if there is a list somewhere, please post. I am trying to get beyond vague 'it's bad' statements and look at the details.

    Bookmark   April 15, 2014 at 10:55AM
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toxcrusadr(Zone 6a - MO)

The Back to Nature CBC website also says:

"In the past, the primary concern with cotton gin waste was arsenic. For years, arsenic acid was used as a defoliant prior to harvesting in most of the U.S. On the High Plains of Texas, early freezes normally eliminate the need for chemical defoliants, and in the rare years where chemical defoliation was needed, sodium chlorate, rather than arsenic, was used. The EPA outlawed arsenic as a defoliant in the early âÂÂ90s and the EPA now requires that all chemicals used on cotton be bio-degradable within two weeks."

I'm not sure what the date is on the paper I posted at the top of the thread but it still lists an arsenic compound. So that might be on the way out if I can verify it.

    Bookmark   April 15, 2014 at 11:09AM
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Have you considered sending an email with your questions to the company? In a reply they will be putting their info in writing, so I would think they wouldn't risk feeding you a line.

    Bookmark   April 15, 2014 at 12:51PM
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"Pesticide" is the broad term that covers ALL pest killers - plant pests (weeds), insect pests, fungal and disease pests, rodents, mites, etc. Herbicides - plant/weed killers - are just as much included under the heading of "pesticide" as insecticides or fungicides.

Here is a link that might be useful: EPA - what is a pesticide?

    Bookmark   April 15, 2014 at 1:01PM
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toxcrusadr(Zone 6a - MO)

Good idea, I'll shoot them an email.

Thanks gardengal, that makes you, me and the EPA at least. :-] I did consult my Funk & Wagnells earlier and it said "specifically, insecticides", but that's out of step with what you're saying. Wouldn't be the first time.

    Bookmark   April 15, 2014 at 4:05PM
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wayne_5 zone 6a Central Indiana

The use of the term pesticide to cover all those 'cides is widespread.

    Bookmark   April 15, 2014 at 4:34PM
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toxcrusadr(Zone 6a - MO)

Well this is interesting! Here is my question to EPA:

"What are the current regulations on biodegradability of pesticides used on cotton? I am trying to answer questions about whether pesticide residues may persist in cotton burr compost. Specifically herbicides that may harm garden plants, but it does not have to be limited to that. I've been told that all pesticides used on cotton must be 'biodegradable within 2 weeks.' I have no verifiable references on this supposed regulation. "

Their response:

'The EPA assesses the environmental fate of all EPA-registered pesticides, but we have no biodegradability regulations, policies or recommendations for herbicides on cotton. With regard to plant damage from manure-based compost, the EPA has received reports related to certain herbicides (e.g. aminopyralid, clopyralid, picloram etc) that have been reported in compost, but our database indicates that these incidents have not been associated with cotton use."

So, the EPA has refuted the claim made by Back to Nature on their website. I wrote to BTN at the same time I wrote to EPA and did not receive a response. I will be forwarding EPA's response to them as a courtesy.

I am now forced to doubt their other claim that arsenic based pesticides are no longer used on cotton. I will have to confirm that elsewhere.

Of course this does not tell us anything quantitative about pesticide residues in CBC, just that one vendor appears to be making a specious marketing claim. More to come.

This post was edited by toxcrusadr on Thu, Apr 17, 14 at 17:11

    Bookmark   April 17, 2014 at 4:52PM
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Arsenic based pesticides/herbicides aren't used much by anyone.

You're going to find agricultural use of arsenic in animal feed (especially poultry), but that's on the decline (only very recently on the decline). As far as herbicides, some areas with really bad pigweed + nutsedge use an arsenic based MSMA...but it's not widely used.

    Bookmark   April 17, 2014 at 5:43PM
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I guess there's no really 'safe' compost to be bought, anymore. I do wonder about the cow and chicken compost--what's in them since the farmers seem to feed them all kinds of carp these days? For awhile some 'all-natural' composts had sewage sludge in them; all technically A-ok. We all will just have to grow our own, I guess.

Thanks for posting your answer from the EPA.

    Bookmark   April 19, 2014 at 6:44PM
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toxcrusadr(Zone 6a - MO)

I think there may be a few composting places where you can find stuff with a relatively low load of residues. For example food waste composting operations are sprouting up, and depending on what they mix in for other ingredients, they may have manure- and sludge-free product. I think that's the best bet.

In my world safety is a relative term - it's all about the dose. There are toxins all over the place (including the fire resistant additives in the plastic in this keyboard I'm typing on). It's very hard to get away from them completely. So I try to control my exposure by hitting the highest contributors first. Perhaps one day toxic chemical use will be so much lower that you won't have to look so hard for what you're seeking.

    Bookmark   April 21, 2014 at 1:17PM
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Thanks for your input, toxcrusadr. I appreciate it!

    Bookmark   April 23, 2014 at 5:27PM
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Very interesting thread, Tox, thanks.

BTW, the bit about the former use of arsenic acid segues with current concerns about rice now grown on those lands, as rice is an unusually aggressive uptaker of arsenic, apparently. Presumably the arsenic is persistent in the soil.

NC or others have comment about this?

    Bookmark   April 27, 2014 at 12:01PM
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toxcrusadr(Zone 6a - MO)

That reminds me, I have not heard anything back from Back to Nature about the wording on their web page.

    Bookmark   April 28, 2014 at 12:53PM
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Thanks for undertaking this project Tox. I look foward to hearing what the EPA has to say,or more specifly what if any meaningful work they are doing in this area. I attempted soliciting them taking action on enforcement of rules they made concurning CFCs and refrigerants in 1990. After 2 years I have seen no action whatsoever. Fact is the extent of what they have done is quote chapter and verse of those sweeping laws and are unable to direct me to the EPA employees who act to end violations. What I found is that EPA has a boat load of people working to inact regulations and few if any going back to see what effect earlier rules are having.

    Bookmark   April 28, 2014 at 3:20PM
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toxcrusadr(Zone 6a - MO)

I hear ya...nothing more frustrating than an 'initiative' that ends up on the shelf. Actually though, quite a few of EPA's regulations are carried out by state agencies. Air, water, waste, landfils, etc. It is sometimes more effective to get hold of someone at the state level, or the Regional EPA office for the region.

I did not feel like we got much back from EPA on that question, but if necessary I could track down someone in FIFRA to get more detailed info.

    Bookmark   April 29, 2014 at 12:02PM
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