Since 2005, thousands of farmers and gardeners who have simply applied compost or mulch to their gardens or fields have unknowingly poisoned their own crops. These tragedies happened — and are still happening — because of potent, persistent herbicides including clopyralid and aminopyralid. Aminopyralid (sold as Milestone, Milestone VM, Milestone VM Plus, Chaparral, CleanWave, ForeFront, GrazonNext, Opensight and PasturAll) was released by Dow Chemical Company in 2005 and was marketed to horse and cattle owners to control perennial weeds. Use of the chemical quickly became widespread, and by 2008, thousands of home gardens in Great Britain perished as a result of herbicide-contaminated "killer compost". In 2009, the problem surfaced here at home, with gardeners and farmers reporting damaged or lost crops from Milestone contamination. The herbicide was rightly pulled from the UK market in late 2008 pending further study — but it was reintroduced in 2010, despite fears from farmers and gardeners.
We’ve been reporting on this widespread problem of pyralid herbicide contamination since it first surfaced. The herbicides end up in gardens and on vegetable farms through what should be a natural cycle — pasture to manure to compost. Here’s what happens: The EPA allows Dow and others to sell these potent weed killers to ranchers, who then spray their pastures and hayfields. When animals graze on the treated pasture or hay, the chemicals pass through the animals and persist in the manure for several years — even if the manure is processed into compost. Gardeners use the contaminated hay, grass clippings, manure or compost on their crops, bringing damage or slow death to plants. These poisons are so powerful that they can damage sensitive crops at levels as low as 10 parts per billion, according to Ohio State University.