Yard waste, specifically illegally sprayed grass, is suspected as a source
The tomatoes grew necks like gourds. The leaves of the purple cornflower, a favorite of butterflies, were twisted and deformed. More plants — cucumbers, peppers, green beans, even the majestic Roselle Hibiscus — began to wither and fail.
Earlier this summer throughout central and western North Carolina, gardeners flooded their neighborhood listservs, Facebook groups and garden stores with complaints: Something was killing their plants, en masse.
“There were a lot of beginner gardeners who were doing this because of COVID,” said Aparna Vanguri, who has a master’s degree in agronomy. She belongs to several Facebook groups that include Indian gardeners living in Cary. “They were asking, ‘Why are my tomato plants curling?’ I thought it might be a virus, but it was too early for a virus.”
The culprit: compost tainted with Clopyralid . Manufactured by Dow AgroSciences, and now its spinoff company Corteva , Clopyralid is a persistent and powerful herbicide. Some states and municipalities have banned it outright. But in North Carolina, it can legally be applied to alfalfa and turf fields, as well on right-of-ways.
The NC Department of Agriculture, which regulates herbicides and pesticides in the state, has opened an investigation. Pesticide Operations Specialist Sydney Ross said the department could not comment because the inquiry is ongoing.
All summer McGill officials have been tracing the source of the Clopyralid. The company posted a note on its website stating herbicides are “never intentionally used in the composting process.” In its online announcement, McGill also said it does not use “any manures, grasses, or bedding from farm animals.”
Annual reports filed with the state by McGill show that it has previously accepted animal waste — 1,544 tons in 2018-19  and 1,306 tons in 2019-20  at its Chatham facility. That waste, though, does not originate on farms, according to state records. It comes from the NC State vet school and labs at the National Institute of Environmental Health Sciences in Research Triangle Park.
McGill President Noel Lyons told Policy Watch that the Chatham facility has accepted a “very small amount of animal bedding is in the form of wood shavings.” The company did detect the herbicide in the bedding material at a concentration of 159 parts per billion, well below the level that could pose risk to human health, 500 parts per million. Last month, Lyons told the EPA the company “immediately eliminated” that source “at considerable revenue loss.”
Yet a small amount of wood shavings could not account for the hundreds of gardeners who have reported their plants had died.
Lyons told Policy Watch that tests so far show a more insidious suspect: yard waste.
Yard waste comprises 10% to 15% of the feedstock the Chatham County facility receives each year, from 14,000 to 15,000 tons. Lyons suspects that lawns are still being sprayed with Clopyralid, in violation of approved uses. After being mowed, the contaminated grass is placed it in yard waste canisters for the city to pick up — and in turn the city sends it to McGill.
It’s unclear which cities sent the contaminated yard waste to McGill this year, and if municipalities themselves are spraying the herbicide on parks and right-of-ways. According to McGill’s renewal permit application  filed Aug. 5, the Town of Cary and Republic Services, a privately owned commercial hauler, sent yard waste to the Chatham facility in 2019.
Now, Lyons said, McGill is working with municipalities that bring yard waste to the facility to exclude grass. “It would be much better if we all left the grass on our lawns,” Lyons said.
Compost facilities in North Carolina must test their material monthly for metals, including lead and arsenic, as well as pathogens, such as E. coli and salmonella. But they are not required to test for pesticides.
The presence of Clopyralid in compost underscores the conflict among the EPA, agribusiness, chemical companies, composters, small farmers and gardeners. Clopyralid has been registered with the EPA since 1987. In 2002, DowAgro Sciences “delisted” it for residential use, but it’s common for people to either misapply or illegally apply herbicides and pesticides.
As part of its routine re-registration process for pesticides this summer, the EPA received nearly 600 comments on Clopyralid, most of them asking for stronger restrictions on its use, if not an outright ban.
Most of the concerns centered on the risk not only to home gardeners, but also small organic farmers whose livelihoods are jeopardized by the contamination.
“The EPA needs to do something about this,” said Frank Franciosi, executive director of the US Composting Council,  headquartered in Raleigh. “It’s not labeled right. It gets in the hands of the wrong people. We think it should be banned for use on all harvesting crops.”
This spring and summer, the US Composting Council received more than 55 reports of plants damaged by the compost in North Carolina alone, according to the group’s database furnished to the EPA.
“I thought this was going to be the year,” said Joanne Andrews of Durham, of her hopes for a bounty of vegetables and flowers. She bought three cubic yards of Certified Soilbuilder from The Rock Shop in mid-May. (The Rock Shop gave refunds to those who notified the outlet that they bought the McGill compost.)
For the first month, she said, “everything looked great. Then I started noticing leaves on the tomato plants that were deformed and weird.”
Clopyralid belongs to a family of chemicals known as picolinic acids, which enter the plants through roots and leaves. The herbicide disrupts the plants’ hormone functioning, stunting their growth and preventing them from sexually reproducing. Tomatoes, sunflowers, potatoes, lettuce and spinach are especially sensitive to Clopyralid, but the herbicide also harms flowers.
Although the EPA has classified Clopyralid as “not likely” to cause cancer in humans, the herbicide is toxic to some beneficial insects, such as ladybugs. It can persists in the soil for at least two years and easily moves through groundwater. It does not break down during the composting process. And it’s hard to detect, said Franciosi, with only two laboratories in the US equipped to do so.
In their comments to the EPA,  representatives from the alfalfa, mint and sugar beet industries, as well as Corteva, all asked the agency to maintain, rather than strengthen the current regulations for Clopyralid. These industries use it to kill weeds, such as Canadian thistle, ragweed and clover, in pastures and farm fields. The companies argued there aren’t effective alternatives for those crops.
But McGill president Noel Lyons told federal regulators they should limit the application of persistent herbicides and to prohibit its use on turf. Only professional licensed applicators should be permitted to use Clopyralid, he said. Pesticide manufacturers should be required to help “remediate contaminated compost and garden soil, and all members of the supply chain should be liable for the contamination: pesticide applicator, landowner, property manager and pesticide product distributor for damages from compost contaminated by Clopyralid.”
Franciosi told Policy Watch that these persistent herbicides erode confidence in the compost industry, which already faces challenges from perfluorinated compounds — PFAS — that have been detected in some of the product. He said the US Composting Council is considering filing a class-action lawsuit against the manufacturer of Clopyralid, the EPA, or both.
The Carolina Farm Stewardship Association advised gardeners who think their plants were contaminated  to contact the state Department of Agriculture , McGill , the US Composting Council  and Toxic Free NC. 
“Persistent herbicide contamination is a decades-old issue for the composting industry,” said Alexis Luckey, executive director of Toxic Free NC. “Until EPA implements tougher restrictions on the use of these herbicides on compost feedstocks, they’ll continue to show up. We need stronger regulation, transparent and protective policies, and more consumer education about compost feedstocks so that growers can make an informed decision about what’s in the soil that feeds their families.”
The NC State Cooperative Extension  recommends tilling and irrigating the affected soil to help microbes break down the herbicide. Gardeners can plant cover crops, like daikon radishes and oats, and then dispose of the entire crop — not in yard waste — once it’s mature. Mushroom compost can also help detoxify the soil.
Jeff Agee bought one cubic yard of Certified Soilbuilder from The Rock Shop. His crops withered, he said, and the leaves “got fiddleheads” — curling and cupping as the Clopyralid coursed through the plants. The cucumbers failed to bear fruit, and Agee pulled his tomatoes early. He did eat from plants that appeared unaffected, he said, “but I don’t blame people if they abandon the whole garden.”
This article has been corrected to remove a reference that McGill is prohibiting yard waste containing grass from entering its facility. The company is working with municipalities to exclude it, but the action is not a ban.