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Killer Compost: New Problems, a New Chemical

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Killer Compost: New Problems, a New Chemical.

We have recently heard reports of continuing incidents of herbicide contaminated compost damaging crops of organic farmers and gardeners. A news report discusses continuing damage from residues of aminopyralid in composted grasses. The report also discusses labeling changes proposed by Dow AgroSciences to help address this problem.

Additionally, we have learned of another "Killer Compost" chemical herbicide. It is called Aminocyclopyrachlor, and this one does come with a restriction on the label.

As we have previously discussed some herbicide active ingredients including clopyralid, aminiopyralid and others are registered for use on pastures. These chemicals can be so persistent that they remain active in the manure that animals pass after grazing on the treated grasses even after this manure is composted. This can create a major problem for anyone who uses the contaminated compost as it can kill or seriously damage broadleaf crops and garden vegetables.

The Washington State University Extension Service reports that herbicide contaminated compost was responsible for "tens of thousands" of dollars of lost revenue for several organic farms, and additional damage to several home gardeners. Tests confirmed the presence of aminopyralid at low levels. The chemical can cause damage to plants at concentrations as low as ten parts per billion (10ppb).

A spokesman for Dow Agrosciences the maker of aminopyralid said that the company had submitted a proposal to the Environmental Protection Agency to address the handling of the herbicide, and that they would be meeting with the EPA shortly. The suggested changes would make it illegal for people in several states to move aminopyralid treated hay or forage grass off the farm where it was applied. A supplemental label however would exempt users in some states.

Another herbicide active ingredient to be aware of is Aminocyclopyrachlor. This herbicide is of a different chemical family than the other killer compost chemicals that we have warned about before, however it has a similar mode of action and a similar risk of persistence in compost. (It is not registered for pasture use however)

Products containing aminocyclopyrachlor come with the following label restriction:

" Do not use grass clippings from treated areas for mulching or compost, or allow for collection to composting facilities. Grass clippings must either be left on the treated area, or, if allowed by local yard waste regulations, disposed of in the trash. Applicators must give verbal or written notice to property owner/property manager/residents to not use grass clippings from treated turf for mulch or compost." (from the label for Imprelis)

At RCC we remain most concerned about these chemicals. The potential to cause harm to unsuspecting farmers and gardeners is very disturbing. Organic farmers and gardeners rely on compost and should be careful of where they get the compost that they use.

The Washington State University Extension Service recommends farmers or gardeners taking several steps to avoid bringing contaminated compost to their properties.

Ask the supplier for information about the origin of the compost and about who the intermediate handlers were. Ask what farm the compost came from and ask for the details of the herbicide practices of that farm. Establish a contract with the compost supplier to guarantee that the compost is contaminant-free. Perform tests for the presence of herbicide contamination. This can be done by growing a test plant in the compost before it is applied to the entire field. For more information please look at our previous news items on Killer Compost. (LINKS)

The Washington State University Extension Service also has information about aminopyralid problems here: