But sitting in a Boston café last month on the eve of his first recreational shop in the state opening in Worcester, Huron said one concern tempered his excitement about his local operations — the prospect of a multimillion-dollar crop failure.

In the 20 years that Matthew Huron has grown cannabis, his business has ballooned from a scrappy garage operation to a company, Good Chemistry, with stores and indoor gardens in Nevada, Colorado, and Massachusetts.

Cannabis cultivators have long quietly griped about Massachusetts’ hard-line ban on pesticides, which prohibits even low-toxicity chemicals widely accepted as safe in other states. But now, as the state’s industry scales up from a medical market to a recreational one with over $120 million in sales, business leaders say they stand to lose far more than before. The ban, they say, could most hurt small and midsize cultivators and potentially cripple efforts to include outdoor growers and farmers in the industry.

Massachusetts has taken the most cautious path on cannabis pesticides among the seven states with legal pot sales. Governor Charlie Baker’s administration cites public health concerns.


Because of federal cannabis prohibition, there is little research on the health effects of pesticide use on pot — which, unlike a tomato, cannot be washed before consumption. Scientists also don’t know the impact of burning and inhaling such chemicals. But one 2013 study published in the Journal of Toxicology found that 60 to 70 percent of pesticide residues on raw marijuana are transferred to the smoke.

Even so, all the other states with marijuana stores — besides Massachusetts — allow growers to use some naturally derived pesticides typically allowed in organic farming.

Last year, the state temporarily shut down Good Chemistry and another medical marijuana provider, Triple M, for using some organic pesticides. Both companies said at the time that their pot was safe and they hadn’t intentionally broken the rules but pledged to comply with the regulations.


Without much-needed guidance from the federal government over which chemicals are safe to use on cannabis, a debate is raging nationwide over how to regulate pesticides. Everyone agrees, however, that any regulation beats the illicit market, where profit-minded dealers often douse plants in toxic chemicals that are intended for decorative plants and that have been associated with cancer and other diseases, according to an April article in Environmental Health Perspectives.

Meanwhile, cultivators say they are being squeezed: They face strict requirements for buds to be free of toxins such as mold and mildew, yet they cannot use the products that they say prevent those issues.

In a recent guidance document by the Cannabis Control Commission, the state suggested cultivators focus on nonchemical methods to control pests, such as cleanliness, good growing practices, and temperature and humidity adjustments.

The Massachusetts Department of Agricultural Resources, which oversees pesticides, said cannabis growers can only use pesticides approved for use on marijuana by the Environmental Protection Agency, which doesn’t address pot because it’s federally illegal.

The state’s Agricultural Resources Department “is committed to ensuring that all pesticides used in the Commonwealth undergo rigorous testing” to protect the environment and public health, said Katie Gronendyke, an agency spokeswoman.

She added that the agency strictly follows the EPA’s pesticide rules.


While the EPA has approved some chemicals for use on tobacco, another smoked plant, the EPA discourages the use of EPA-registered pesticides on products not specified on their labels, such as marijuana.

The state agency said it has reviewed other states’ pesticide policies for cannabis.

Every other state with pot shops publishes a list of approved pesticides or specific guidelines for what’s allowed. In contrast, the Agricultural Resources Department’s policy, published online in September, strikes some cannabis companies as unclear.

The policy states that “the use of pesticides on marijuana or hemp is prohibited in Massachusetts.” The policy acknowledges that using certain pesticides deemed “minimum risk” would not violate state regulations but doesn’t specify what they are, adding: “it is important to understand that the use of any product is done at the risk of the grower without the benefit of review and testing by the EPA to determine health and safety or other impacts.”

The Commonwealth Dispensary Association, which represents medical marijuana operators, has asked the state to change its policy to mirror those of other states.

“We hope that they look at other states’ experiences and adopt similar regulations,” said executive director David Torrisi, “that allow for the use of some pesticides for cannabis cultivation.”

In Colorado, which became the first state to begin recreational pot sales in 2014, regulators initially banned all pesticides for the same reason as Massachusetts — the lack of guidance from the EPA, said Ron Kammerzell, who oversaw Colorado’s marijuana enforcement from 2012 to 2017.


When the state began testing pot for pesticides about two years into recreational sales, they found that most crops failed.

The contaminated plants were seized.

“Obviously, our industry was up in arms,” Kammerzell said. He said growers felt hamstrung in their efforts to pass all the required tests, asking: “‘How do we control all the toxins you’re testing for, like mold and mildew, and pass those tests when you won’t let us use pesticides?’”

Regulators deployed a mixture of enforcement, collaboration, and education, he said, and with industry input developed a list of approved chemical pesticides, mostly naturally derived oils and soaps, that were deemed relatively safe. The three pesticides that Good Chemistry was cited for are all allowed in Colorado as well as in Oregon, Washington, Alaska, and Nevada.

“These kinds of pesticides are used on edible plants,” Kammerzell said. “They don’t have high levels of toxicity and don’t tend to stay within the plant after a period of time.”

Now, the fail rate for marijuana companies has plummeted, he said.

Good Chemistry’s chief executive, Huron, said he thought Colorado had arrived at a good policy.

“It’s easy for a lot of things to go wrong” when growing marijuana, Huron said. “Farmers need tools to be successful.”

Massachusetts’ current situation is especially tough on outdoor and greenhouse growers who wield far less control over insects, humidity, and temperature, said Suehiko Ono, cofounder of Eos Farm in Pittsfield, which is seeking to become a licensed outdoor cannabis cultivator. So far, the state has licensed only one outdoor grower.


Now that legal pot must be grown in-state, Ono said, policy makers should incentivize outdoor growing because that would help spur a craft cannabis market. Nathan Klima for The Boston Globe

Now that legal pot must be grown in-state, he said, policy makers should incentivize outdoor growing because that would help spur a craft cannabis market that could better compete with big national conglomerates.

“If it’s grown in the sunshine, in Massachusetts soil, with Massachusetts water, by Massachusetts farmers, that is real local,” Ono said. More outdoor growing could bring more farmers into the industry, one of the state’s goals, he said, and lead to Massachusetts becoming known for a distinct flavor of cannabis akin to the famed wine produced in Napa Valley.

Ono plans on having his cannabis retail space in what is now Royal Cleaners in Pittsfield. Nathan Klima for The Boston Globe

Cannabis Control Commissioner Kay Doyle, an environmental working group member, said she’s sympathetic to farmers and small businesses but pesticides are solely the domain of the Agricultural Resources Department, which “came to the conclusion they felt was in the best interest of the Commonwealth.”

“The best thing that could happen is the federal government reevaluate its policy,” Doyle said, which would spur research on what’s safe.

But some say waiting for the federal government could take many years.

“I would encourage [Massachusetts] to look at best practices in other states — you don’t really need to reinvent the wheel,” said Kammerzell, the former Colorado enforcement chief. “It’s a balancing act between public health and making sure you’re giving your operating licensees the ability to succeed.”

Naomi Martin can be reached at naomi.martin@globe.com. Follow her on Twitter @NaomiMartin.