Gardeners in Vermont got a nasty surprise this summer when they used compost purchased from a local county: It killed their plants. A scientific hunt ensued, but the true culprit has been elusive.
The problem emerged in June, when gardeners in the greater Burlington area who bought the Chittenden Solid Waste District's Green Mountain Compost found their plants were wilting and dying. District manager Tom Moreau was among them, and suspected that his compost was the cause, the Burlington Free Press reported (cached article).
Both bulk and bagged compost were tested by the firm Anatek and initial results revealed small amounts of the herbicides Clopyralid and Picloram. Customers were notified and sales halted. However, Clopyralid's manufacturer doesn't allow residential use. Picloram requires licensed applicators, but no one had used it commercially in the state since 2009.
"We are baffled at where this could be coming from and are working with the state to track its source," Moreau told the public in early July. Officials wondered if the cause might be the illegal use of weedkillers.
Last month the mystery deepened. The Chittenden Solid Waste District (CSWD) sent more compost, as well as manure, grass clippings, and a national brand of horse feed that local farmers use, to get tested with another company, Carbon Dynamics. Horse manure was a compost source.
This time no traces of Clopyralid or Picloram were found in preliminary tests, but an herbicide called Imprelis was detected, the Free Press reported. This was especially strange since Imprelis was only on the market briefly before being pulled last year over safety concerns. Usually the state lab would do all this testing, but it's still recovering from Hurricane Irene.
I grew up in Burlington, and my mom, an avid gardener herself, first alerted me to this local news story. Recently the story went national when the Environmental Protection Agency agreed to help. Testing continues. Meanwhile, the CSWD is spending $1 million on customer reimbursements and studying how this could have happened. Who knows how much more dirt there will be.
Photo: Compost at the Chittenden Solid Waste District was screened for herbicides over the summer. Credit: Shawn Wright, Waste & Recycling News.