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poison compost?

A neighbor is willing to let go of his lawn cuttings, but he uses pesticides once a year on his lawn. The cuttings are valuable, but the use of pesticides worries me as I am trying to reestablish micro organisms back into my garden soil. The neighbor claims the pesticide isn't heavy duty stuff. Should this compost be used or left alone?

Greener Thumb
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Joined: Mon Jun 22, 2009 3:00 pm
Location: Austin, TX

How long ago was the pesticide used? If it's been over a month or so then I'd say it's fine. Pesticides eventually wash off, wash away or the grass will grow out and there won't be any left. If it's been used recently, then I wouldn't use it. Others might have different opinions, and it in the end it also depends on what pesticide was used. Let's see what others say.

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Agreed: find out what the neighbor uses, when it was applied, and how it was applied (sprayed? soaked? granules?--this may give information re. quantity per square foot).

Then look up the decay/degradation rate of the toxin and (in my opinion) double it as a safety margin. Example: if the decay rate is listed as 30 days, wait 60 days before glomming onto the grass clippings. Then take all of 'em you can get.

Hope it all works out!

Cynthia (Vergil came home from TPLO surgery tonight and the work deadlines just keep coming)

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Location: Lexington, KY

Interesting. I am using my grass clippings, and I applied Scotts Weed and Feed twice this year, once in February and once in March. I started mowing in early April. Am I at risk for damaging my garden? Don't pesticides also degrade / wash away during the time that the grass is decomposing in the compost pile?

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Location: Zone 7

Thanks - this is just the info I'm looking for. I have access to tons of grass clippings, but with who-knows-what sprayed on them.

If I age them until next spring, I should be good to go.

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stephenabney wrote:Don't pesticides also degrade / wash away during the time that the grass is decomposing in the compost pile?
In most cases they should, but if you want to ensure there isn't any, then its always best to keep them out in the first place.

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stephenabney wrote: Don't pesticides also degrade / wash away during the time that the grass is decomposing in the compost pile?
Plants that contain natural toxins, e.g., rhubarb leaves, do decompose and lose their toxicity in the compost pile.

However, grass clippings which have *recently* been treated with PESTicides will, as a matter of course, kill many of the organisms which work on the compost "ingredients": springtails, pillbugs (aka rolly-pollies), earwigs, and all. I can't imagine that the PESTicides will be all that kind to other, non-arthropod organisms in the compost pile, either. That's why I recommend letting the toxins degrade in place and then using the clippings.

Sure, some of the "compost critters" will survive, but why mess things up for them when you have the option not to? Just mark on the calendar when twice the degradation period (assuming that what you're using *does* degrade...) will have passed, and then start using the grass clippings.

If this is too much of a pain, there are alternate approaches to lawn maintenance in our Landscaping and Lawn forums; maybe that would be useful? :)

Cynthia (Vergil came home from TPLO surgery last night, I'm working at home this holiday weekend, those work deadlines keep coming...)

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heya scrub,

I told you this place gets you good advice fast!

I concur with a "reverse IPM" approach. Knowledge is power, and the first step too. So make sure you find out what went in.

For good voodoo measure I would treat the lot with strong EM that's been brewed with strong light. Who knows, the PNSB may help break down any hydrocarbons and who knows what else.

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Location: TN. 50 years of gardening experience.

I am afraid to take chances. If in dought I never use it.

Would you like to have some 2,4-D with your dinner?

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I have been at my present location for five years. The lawn where my garden is was heavily sprayed. There wasn't a weed in it. This year was the first year we saw worms. We have been dumping all the grass and leaves on every year. Plus loads of horse manure. (many, many loads). I had a decent garden this year and I would never put treated grass clippings on. It just isn't worth the risk.

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There is a difference between pesticides and herbicides. Pesticides work mostly on insects and if you wait long enough, they are broken down, mostly by soil organisms and would be o.k. to put in the compost pile.

However, herbicides kill plants. Round Up is absorbed through the plant leaves deactivated by soil organisms once it hits the ground, and broken down quickly which is why with glyphosate only, you can plant again after three days. Extended control products are another story. Some of those can remain active for a year or more depending on how they are combined.

Compost containing herbicides like 2,4,D can persist in the compost and will show up as herbicide damage on your plants. If an herbicide was used, then it is better not to put it in the compost.

Herbicide residues don't always come from the neighbors grass clippings. Homeowners usually don't have access to the heavy duty stuff. However commercial golf courses, farms, and pastures may use use them. Herbicides usually do not affect animals since they work on a different pathway that only exists in plants, however the pesticides on the grass or field may be eaten by the animals and be excreted in urine or manure. If you are applying manures from treated fields, they may also contain herbicides. Another reason why I prefer not to use animal by products.

Not all herbicides last that long. Regular glyphosate has a 60 day half life and no preemergent activity. Herbicides containing clopyralid, picloram and aminopyralid cause the most problems. It is usually the result of spraying plants in pastures, on farmes, golf courses, and some of your neighbors can be using it on the lawn. The more insidious culprit is not the plant residues but manures from animals that ate the sprayed plant materials as the herbicides are concentrated in urine, feces, and by the composting processes.

When in doubt, keep it out. ... glyphosate ... lyphos.pdf

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As an environmental chemist and haz waste expert, my rule of thumb is, never put fresh mystery grass clippings directly on the garden as mulch. If they've been treated - especially sprayed - herbicides can damage your plants.

Virtually all products used on yards will decompose in the compost. I have never had trouble composting grass clippings.

The only thing to be concerned with is a few persistent herbicides that are used essentially only by farmers and professional applicators. Usually on pastures. [Edit: I see this was covered above] They can persist into hay and thence to manure. Takes about 2 years to break them down. If you're interested look up chlorpyralid and picloram and 'toxic compost'. But if you ask your neighbor and he's used regular 2,4-D, dicamba etc. weed and feed, compost those grass clippings. Today's pesticides have been selected to biodegrade pretty rapidly, so that they don't cause the kinds of problems DDT did.

As far as toxicity to humans, keep in mind that unless you're eating all organic vegetables, you're exposed to tiny amounts of this stuff and those levels are deemed safe. Also, toxins have to be absorbed into plants and into the part you eat, which is not a 100% efficient process. Far from it. I don't see the problem with grass clippings in the compost.

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