SOURCE: The Counter

DATE: July 22, 2020

SNIP: Clopyralid, used on golf courses and large-scale hayfields, is ending up in compost—and ruining plants that grow in it.

In late April, [Iris Nason] moved her tomatoes into the outdoor beds, containing new soil from a local supplier. A week later, she knew something was wrong.

Her healthy starts were twisted and the leaves began curling and cupping into strange shapes. Nason is a long-time gardener but had never seen anything like this before. She posted photos in a local gardening group and discovered many others were experiencing similar things with their gardens.

They all had one thing in common: the company they’d gotten their soil amendment from—soil that had been contaminated with the herbicide clopyralid.

This herbicide, along with aminopyralid and picloram and a few other varieties, are all known as “persistent herbicides” because they take a long time to break down. All of them are commonly used on golf courses and hayfields where they’re deployed to kill problematic broadleaf weeds. Even though state rules (which vary) are supposed to prevent clopyralid-contaminated grass, wheat, or other clippings from ending up in compost, cases like the one in Portland are not uncommon. If an animal like a horse or cow eats feed that has been sprayed with clopyralid, the herbicide can pass through the digestive tract and come out in the manure still active, according to the Oregon Department of Agriculture. This contaminated animal manure can also make its way to local composting companies.

Clopyralid leaves grass or hay intact while killing pesky broadleaf weeds like thistles and dandelions, according to Rick Carr, farm director and compost specialist for the Rodale Institute, a nonprofit that researches organic farming methods. This has led to its popularity on everything from rangelands and pastures to golf courses. But it’s now finding its way into compost facilities through clippings from sprayed lawns and clopyralid-laced manure.

“If you’re a compost facility it’s a serious concern.” Carr is aware of the issue and has stopped accepting any manure from horse farms as a precaution against -pyralid damage in the compost he creates. “The average person has no clue about this,” Carr says.

Clopyralid can negatively affect plants at concentrations as low as three parts per billion, according to the U.S. Composting Council (USCC). “It’s getting into our facilities without us knowing it,” says Frank Franciosi, executive director of the USCC. “Not everyone who has an issue realizes they have an issue,” says Franciosi, referring to gardeners with contaminated soil and composters alike.

The problem of compost contamination first came to light in 1999 when tomatoes growing at a compost facility in Washington state showed signs of clopyralid toxicity. Between 2000 and 2003, contaminated compost was also detected in Ohio, Pennsylvania, New Jersey, and California. Dow Agrosciences, which produces clopyralid, discontinued registration for residential use (which meant homeowners couldn’t use it in their lawns or backyards) in 2002 to prevent compost contamination. USCC had gotten reports of roughly five incidents a year of persistent herbicide damage in the United States until this year when there were sixty-nine. And many people believe this is only a fraction of the overall problem.

“It’s only brought to my attention if somebody complained and came to us,” says Jon Traunfeld, an extension specialist in Maryland. “But the symptoms are alarming,” he says of tell-tale signs of -pyralid damage like leaf cupping and stunted growth. This year’s first case of clopyralid contamination came to his attention in June though it’s far from the first time he’s encountered it. “In Maryland, the Department of Agriculture does regulate compost,” Traunfeld says, but the main concern is the presence of toxic heavy metals like mercury and lead or coliform bacteria like E.coli. While those are both hazardous to human health, for many gardeners—especially ones who grow organic produce—finding out that herbicides have tainted their plants is comparably alarming. Few people want to eat produce from -pyralid afflicted plants even if the plant survives enough to produce fruit (which doesn’t always happen). Of food crops, nightshades like tomatoes and legumes are the most sensitive to even trace amounts of clopyralid. “I don’t know of any cases where the plants recover,” Traunfeld says.