Wednesday, July 6, 2011

Beware of herbicides in compost

In light of recent news that Roundup and similar glyphosate weed killers cause birth defects, it is important for all of us who manage weeds on our properties to realize that common weed killers are often not "harmless" as advertised. The Pesticide Action Network of Blaine County is setting an example for private property by developing and encouraging integrated pest management at schools, parks and public places.

I purchase locally grown hay and feed it to my horses. Horse waste is put in my compost pile, along with lawn and yard clippings. Last year, we used the compost on our vegetable garden. As the plants came up, I noticed something very wrong. Most of my vegetable plants were extremely deformed. The potato plants resembled ferns, with the leaves twisted and the stems clubbed. Tomato and sunflower blossoms and stems were almost unrecognizable, they were so abnormally shaped.

I sent plant samples to the state food lab in Twin Falls. The chemist there told me that the damage was indicative of that caused by a class of herbicides now commonly used on pastures, roadsides and hay fields. These herbicides are clopyralid and aminopyralid and their related compounds. According to an Ohio State University fact sheet, clopyralid, is sold under the trade names Reclaim, Stinger, Transline, Confront, Lontrel, Curtail and Millenium Ultra.

Clopyralid is very persistent in composts and manures and is largely unaffected by the composting process—plants in the bean family, the potato/tomato family and the sunflower family are very sensitive to this herbicide. It can stunt these plants at levels in compost as low as 10 parts per billion! Since the level of clopyralid on grass the day of application is 10,000 to 50,000 ppb, even a small amount of contaminated material can cause major problems." Go to to check these facts.

My horses ate the contaminated hay and the composted manure was still able to severely damage my vegetable plants years later. Although there are assurances that the remaining residues are not harmful to humans, there were similar assurances from Monsanto about the safety of Roundup, which is now shown to cause birth defects. The damage from herbicide residue in my garden was costly, both in time and money spent on my heretofore-unsprayed garden.

I understand that local farmers and lawn services are trying their hardest to produce the best product, and are encouraged to use these herbicides, probably without knowing how they break down. I suggest that others who buy hay or have their yards sprayed ask if these herbicides are used, and encourage their farmer and lawn-care friends to use shorter-lasting products, or better yet, use integrated pest management.

In addition, the city of Hailey could adopt the Pesticide Action Network's policy for safer weed management on our public parks to set the right example.

For more information, go to

Lili Simpson


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