Contaminated Compost: Coming Soon to a Store Near You

Reader Contribution by Staff

In Santa Rosa, Calif., the folks at Grab n’ Grow have been making compost and planting mixes for 25 years, using organic materials generated in Sonoma County. In 2002, the company detected residues of a potent herbicide called clopyralid in a batch of compost. The next year, Grab n’ Grow manager Don Liepold and his wife saw the herbicide’s trail of destruction in their raised bed organic garden — lettuce that refused to grow, curled and wilted peas, and stunted, gnarled tomato leaves. 

As we reported in July 2009, clopyralid and its close cousin, aminopyralid, easily persist, sometimes for YEARS!, in hay, manure and compost. When contaminated materials are used in food gardens, tomatoes, beans and other sensitive crops develop curled foliage that looks like a disease, if they grow at all.

Both herbicides are manufactured by DowAgrosciences, which seems to have no moral or ethical problem selling products which clearly are polluting the public compost stream. Meanwhile, aminopyralid pesticides have been pulled from shelves in the United Kingdom. Liepold, the Rachel Carson Council and MOTHER EARTH NEWS think the U.S. EPA should take the same action here.

“I have been testing  and detecting herbicide residues and thus rejecting cow manure, horse manure, turkey mulch, rice hulls, mushroom compost and yard trimmings,” says Grab n’ Grow manager Don Liepold. “I spent $20,000 in lab fees in 2008, and am on the same track for 2009,” he says.

It is extremely difficult to keep contaminated materials out of commercial compost. “One load of contaminated grass clipplings can ruin a batch of compost,” says Eric Philip of Anatek Labs in Moscow, Idaho. Philip has seen so many positive tests for clopyralid residues in compost that he would not use untested compost in his own garden.

“When folks have plants die in their home gardens, their first assumption is that they did something wrong,” Philip says. But with pyralid-laced commercial compost becoming more common, contaminated soil amendments are often to blame.

The source of pyralid pollution can be impossible to trace. For example, a horse stable may use hay brought in from a neighboring state, without knowing that it is laced with pyralid herbicides. If the horse’s manure or stable litter ends up in a garden, disaster is ready to strike. It’s better to be safe than sorry. Liepold stopped making one of Grab n’ Grow’s most popular products, Mango Mulch, for more than a year because he could not find an uncontaminated manure supply. Now he’s getting it from two local organic dairies.

Testing for contamination is a slow, painstaking process that comes at a steep price of $350 (or more) per sample, so most commercially-made compost is not tested. 

Both of these herbicides were approved by the EPA before their persistence in compost was known, and before lab tests existed that could detect residues at damaging levels.  We think approval of these pesticides should be revoked before the damage gets worse.

To express your concern about this hidden danger to your garden, write to your senators and congressional representatives to make your voice heard. You can also contact Rick Keigwin, director of the EPA’s pesticide review division.

See our earlier report: Milestone Herbicide Creates Killer Compost for lots more background on this issue.