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clopyralid half life: 11 years or 11 months

 
paul wheaton
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One of the readers here sent me an email asking me for my source for stating, so many times in the past, that the half life of clopyralid is 11 years. 

My source on that was a bunch of research in 2001.  I think there were several articles and I interviewed some folks at some composting facilities.  But I thought google would back me up. 

Nope. 

The information I was finding was showing a half life of months, not years.

While I am quite certain that I confirmed "11 years" from more than one reliable source in 2001 I am prepared to concede it now.  Perhaps my sources had poor information? 

At this point, I'm gonna sit on the fence and say "I was convinced it was 11 years, but new information has a strong indication of 11 months - sometimes less."

Normally, I don't like to talk about pesticides in these forums.  But there are two that I'm aware of that can have a big impact on organic practices due to lasting many years in the soil.  Clopyralid is one.  Picloram in another.

My impression is that once these get banned, then the chem companies come out with something new that has not (yet) caused as much damage and is the replacement product.

I wanted to set this thread up to make folks aware of my probable error and in the hopes of fostering better information gathering to get a more accurate answer.


 
Gordon Hogenson
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The Internet research I did on clopyralid indicated that it would mostly decay out over a year or so.  One important factor is that you don't have to rely on the vagaries of studies, you can test your compost with a bioassay.  Grow some peas in regular potting soil and in your questionable compost or soil.  If the peas grow normally, your soil is not contaminated.  If the peas grow all crinkly and funny, then the soil is contaminated.

See: http://www.puyallup.wsu.edu/soilmgmt/Pubs/CloBioassay.pdf
 
Leah Sattler
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pesticides may not be a fun subject but they are a reality that we all need to be aware of. we may not use them ourselves but they are all around us and we need good reliable information on them. Their known side affects and rates of decomposition are important for us to know. especially because few people are going to be able to avoid them entirely since they can come in on purchased food, purchased garden supplies, exist in the soil at new properties, be washed down onto your property etc....I want to know the ones that are especially bad so as to direct my efforts to their avoidance rather then chase a bunch of rabbit trails worrying about some things when I should be worrying about others. for instance I can't possibly buy organic hay. its just not happening...probably ever......so I want to know what questions to ask to get the best hay with the least contamination.
 
paul wheaton
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I think the best question is "does it contain weeds?"  They will feel it is a strong selling point to say "no" even if it does.  If they say "yes", then you are doing business with someone honest.  Then ask about if the land/hay has been sprayed.

 
Joel Hollingsworth
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Leah Sattler wrote: I want to know what questions to ask to get the best hay with the least contamination.


Hmm...my intuition is that you might get the best information by saying you might plant (or have planted) a tiny (by their standards) plot of the same hay, then asking how they control X problem, in a way that is consistent with (but not necessarily claiming to be) a grower who might be interested in spraying the same chemicals.  If you're lucky, they might even tell you the exact days and rates of application, or show you their whole schedule.  They'll have a business incentive to make growing hay seem complicated and expensive, and from what I gather, people like to talk about the way they grow things. 

Once you have brand names, you can often use a search engine to find out a lot.  Typing in the name of a pesticide might get you a Wikipedia article with concerns, links to news articles etc., but will at least give you the generic name of the chemical.

As the title suggests, you might be able to type that generic name back in, along with "half life," and you can see how quickly it decays.  The generic name plus the species name of a plant you wish to grow might bring up a few abstracts from scientific papers; even if the full journal article is behind a paywall and not accessible, reading the snippets of text from the search engine results page should give you an impression of where you stand, phrases like "showed no effect" or "controlled up to 5th leaf stage".
 
Jennifer Smith
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There are dead spots still on the plantation where the previous bioligist sprayed stuff.  I have no idea what all they have done out there but some of it was not good.  They still use a lot of sprays and it will be a hard habit for my other half to break.  Permaculture can be an uphill battle..who would have thought?  Logic has been lost to many farmers and their teachers.
 
Leah Sattler
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paul wheaton wrote:
I think the best question is "does it contain weeds?"  They will feel it is a strong selling point to say "no" even if it does.  If they say "yes", then you are doing business with someone honest.  Then ask about if the land/hay has been sprayed.




that is an excellent strategy. that is along the lines of what I do now. avoid ads that talk up the hay or talk about being weed free. nice thing about goats....weeds are not bother. I want the junkie hay from overgrown feilds and will ask for it! I suppose they think I'm nuts but who cares.
 
paul wheaton
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As the weeks have passed since I have posted this ...  I got to second guessing this new information. 

1)  What if the accurate half life is 11 years, but that makes somebody look bad, so they push out formal-looking info that says 11 months instead. 

2)  For all of those professional composting operations that got shut down, it would seem that the stuff that might have clopyralid in it would be stuff like the grass from lawns, or twigs/leaves from trees.  Could that be more than 10%?  And it would probably take them at least 90 days to go from cut from some property to selling it as finished compost.  And yet people still had gardens die.  And for all of the plant material that was contaminated, how much time passed between the time that the clopyralid was sprayed and the times that the organic matter went to the coposting company. 

3)  If the half life was only 11 months rather than 11 years, it would seems that those compost companies could still be in business just by keeping some of those compost piles much longer.  They could toss pea seed on the piles once in a while and when the peas do well, they then sell it.  Instead, those companies went out of business.

 
paul wheaton
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Another question:  clopyralid is now banned.  But I have a vague memory that since it was banned, the same company keeps coming out with new stuff that is a lot like clopyralid - and they sell big heaps of that until that is banned.  Then they just come out with another one.    Has anybody seen any validation of this wickedness?

 
Leah Sattler
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generally it does seem to work something like that. with any new product. they found a chemical mechanism that works to accomplish some very narrow goal (kills bugs, lowers cholesterol, tastes sweet with no cals etc...) then when the problems start to arrive they try to take out or change whatever portion of it is dangerous or problematic and leave the part that works or find something similiar (and they hope is less dangerous) that utilizes the same pathways they found to the goal, and have another go at it with a slightly different but similiar compound or method. gee. no one stops to think if there is a way to head off the initial problem to begin with using benign techniques.

it might go something like this......wow! cool discovery! this little chemical compound keeps the insects from molting and maturing by interfering with x part of the metabolism by attacing to receptor Z. but higher lifeforms don't have receptor Z so it doesn't affect them. release product. ooooh wait. oops this also causes serious problem Y. well lets see if we can find something else with similiar action that interferes with x part of the metabolism and prevents molting too 'cause that worked pretty good in stopping the lifecycle (or maybe something that interferes with some other crucial portion of their bodily function or lifestyle)...........product #2 comes out.......and it goes on and on....
 
paul wheaton
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Hmmmm .... it sounds like clopyralid is still sold in france.

A couple of newer and similar herbicides:

Triclopyr

Aminopyralid

 
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