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Public Radio's Environmental News Magazine (follow us on Google News)

Killer Compost

Air Date: Week of

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Gardeners in the Pacific Northwest are having a problem with contaminated compost. Some of the compost contains an herbicide that kills plants. Host Steve Curwood speaks about the problem with Seattle Times environmental reporter Lynda Mapes.


CURWOOD: With spring approaching, it's time to start thinking about growing vegetables again, but for some folks in the Pacific Northwest there's an unexpected hazard to avoid. Instead of helping plants, some lawn compost is killing them. The culprit turns out to be an herbicide called clopyralid, which is applied to hay and grass that's later turned into compost. Clopyralid has been used since the late 1980s, but mandatory composting programs, in its popularity among growers, make it a pesky problem in Washington State. Lynda Mapes covers natural resources and the environment for the Seattle Times. Welcome, Lynda.

MAPES: Thank you.

CURWOOD: Now, I understand that this contaminated compost has killed garden favorites like tomatoes and beans. Can you tell us about the herbicide that is apparently causing the problem? How is it normally used?

Photo courtesy of Seattle Public Utilities(Photo courtesy of Seattle Public Utilities)

MAPES: It's made by Dow AgroSciences and it is typically purchased by professional lawn care services or by farmers. The point is, this stuff kills weeds very, very effectively and very selectively, in very, very small concentrations. And the problem is, the chemical persists on the clippings, and when they are collected and taken to a composting facility, the chemical persists more than a year and therefore winds up in compost.

CURWOOD: Now, how is it that people find out they have this problem?

MAPES: Well, their plants die. It could be confused with other sorts of problems, such as salinization, but, if you know what to look for, it's unmistakable. The plants twist, and the stems are misshapen. The plant is badly stunted. It won't set a flower. It usually won't make a crop.

CURWOOD: It sounds like what happens to me when I set my plants out.

MAPES: (laughs) You know, it's interesting you say that. One of the reasons folks perhaps haven't seen this problem come to the fore until now is that a lot of gardeners, if things don't go well, they figure, Well, it's just me. And it really could be that more people are actually having trouble with this than is known at this time, because they're not recognizing the problem for what it is - herbicide contamination.

CURWOOD: Now, what does Dow say about this problem? Do they know how long it will persist and what might be done about it?

MAPES: Dow is saying, "We label our product and say clearly on that label that material that's been treated with clopyralid should not be used for compost within one year of application." So basically what they say is, "People are having this trouble because they're not using this chemical in the way that we say it should be used."

CURWOOD: What about the longevity? What evidence is there that, in fact, it goes away after a year?

MAPES: Well, this is the thing. Dow is, I think, as puzzled about this as everyone else, or so they say. The chemical is thought to degrade, if sprayed on soil, within a couple of weeks' time on average. However, in compost, they at this time say they do not know, just flat have no idea, how long it takes for the material to degrade.

CURWOOD: Now, what is all this doing to the composting industry in Washington?

MAPES: It's a mess. There is a lot of concern on the part of the composters because they sell this material to the public and the public, at this point, is wary of a material that's always been regarded as the mother's milk of soil. There's a lot of irony here. Composting has come to the fore as the heart and soul of sustainable agriculture and more progressive sort of lawn management. It's just a big surprise to people that something they've always thought of as being beneficial could potentially be killing their plants.

CURWOOD: Now, what is the State Department of Agriculture in Washington doing about this? I gather that given the level of concern out there that some action is imminent.

MAPES: It's true. The goal is to set new regulations governing the use of clopyralid just in Washington state by April 1, the beginning of the growing season. A draft regulation has come out and it could still change before that date. The chemical is registered by the EPA and it's no easy matter at all to either curtail or in fact ban the use of a chemical once it's registered. But the draft, at this time, as it's currently envisioned, would ban the use of clopyralid on residential lawns. You could still use it in the agricultural applications, where growers say that they really want to continue to have access to this chemical.

CURWOOD: Lynda Mapes is a reporter with the Seattle Times. Thanks for taking this time with us today.

MAPES: You're welcome.

[MUSIC: Ofaria, "Big Bang"]



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