McGregor Scott, the United States Attorney for the Eastern District of California, speaks Jan. 23, during a news conference in Sacramento, Calif. Researchers and federal authorities are finding what they say is an alarming increase in the use of a powerful pesticide at illegal marijuana farms hidden on public land. (AP Photo/Rich Pedroncelli, File)

McGregor Scott, the United States Attorney for the Eastern District of California, speaks Jan. 23, during a news conference in Sacramento, Calif. Researchers and federal authorities are finding what they say is an alarming increase in the use of a powerful pesticide at illegal marijuana farms hidden on public land. (AP Photo/Rich Pedroncelli, File)

Study: Deadly pesticide use increases at illegal pot farms

Most of the illegally grown California pot is destined for Midwestern and Eastern states.

By DON THOMPSON

Associated Press

SACRAMENTO, Calif. — Researchers and federal authorities are finding what they say is an alarming increase in the use of a powerful pesticide at illegal marijuana farms hidden on public land in California.

The pesticide residue is showing up in about 30 percent of the plants themselves, researcher Mourad Gabriel told The Associated Press.

Most of the illegally grown California pot is destined for Midwestern and Eastern states, federal prosecutors said. Federal and state authorities are announcing Tuesday that they will target the illegal grows with $2.5 million in federal money.

Researchers found the highly toxic pesticide Carbofuran at 72 percent of grow sites last year, up from 15 percent in 2012, said Gabriel, executive director and senior ecologist at Integral Ecology Research Center and one of the few researchers studying the ecological impact of illicit grow sites.

California has long allowed medicinal marijuana, and this year legalized recreational pot. While U.S. Attorney McGregor Scott will continue to enforce federal marijuana laws, he said he is targeting illicit grows on public land with cooperation from California’s attorney general and the state’s National Guard.

“What is happening here is illegal for all purposes under anybody’s law,” he said in an interview before Tuesday’s announcement.

One of the dangers before legalization was that users could not be sure what was in the product they were smoking or eating, but authorities say the rise in Carbofuran use poses an increased danger.

The chemical is intended for use as an insecticide but is so powerful that a quarter of a teaspoon can kill a 300-pound (136-kilogram) bear, Gabriel said. Research by Gabriel and colleagues previously showed that the use of pesticides at illegal marijuana farms is poisoning significant numbers of California’s few hundred remaining fishers, a threatened carnivore.

Carbofuran can’t legally be used in the United States, and every bottle found at the grow sites since 2012 has been labeled in Spanish, Gabriel said.

Scott said it is being smuggled in from Mexico by drug cartels and the itinerant laborers hired to clear forestland and replant it with marijuana. The laborers have to pack in the plants, fertilizer, irrigation hose and camping supplies for the summer growing season.

Laborers apprehended by authorities tell Gabriel the remoteness of the growing sites is one reason highly toxic Carbofuran is so popular.

“What they are saying to us is this is extremely effective — it takes a little amount to kill a deer or a bear — so we don’t need to bring a lot of it to last a season,” he said.

At normal levels, a typical bottle containing less than 1 liter should be diluted with up to 5,000 gallons (18,927 liters) of water, he said. But illegal growers are diluting it with just 3 to 5 gallons (11 to 19 liters) of water to spray plants, or using the concentrate directly to kill wildlife.

At that concentration, the chemical takes at least 2 ½ years to dissipate instead of roughly a month if it is used at recommended dilutions.

Talk to us

> Give us your news tips.

> Send us a letter to the editor.

> More Herald contact information.

More in Northwest

The Washington state Capitol. (Photo by Bill Lucia/Washington State Standard)
Debate flares over WA child welfare law after rise in deaths and injuries

A Democrat who heads a House committee with jurisdiction over the policy says the Keeping Families Together Act may need to be revisited during next year’s legislative session.

Ferguson said the state would, “not be bullied or intimidated by threats and legally baseless accusations.” (Photo by Bill Lucia/Washington State Standard)
WA ‘will not be bullied or intimidated,’ Ferguson tells Bondi

The governor on Tuesday responded to a letter from the U.S. attorney general warning the state over its “sanctuary” immigration policies.

WA fire officials press for safety reforms amid accessory dwelling unit surge

Some units are getting squeezed onto lots without enough space to get emergency equipment to front doors. They seek changes in the state building code.

Paramedics and first responders attend to one of two injured workers at a worksite in 2024. Interpreters for the state Department of Labor and Industries serve those injured while working for an employer that is self-insured and does not participate in Washington’s workers’ compensation system. (Duck Paterson photo)
Washington interpreters demand state address more than $280K in missed payments

The state Department of Labor and Industries doesn’t pay these interpreters directly, but they say the agency could pressure companies to properly compensate them.

A ‘no trespassing’ sign on a fence outside the Northwest ICE Processing Center. (Photo by Grace Deng/Washington State Standard)
Tacoma detention center must pay for violating minimum wage law, appeals court affirms

The facility’s for-profit operator has argued it shouldn’t have to pay Washington minimum wage to immigrant detainees. An appeals court on Wednesday disagreed for the second time.

In all of 2024, the total number of Washingtonians with concealed carry licenses increased by fewer than 6,000, compared to about 14,000 already this year, state data show. (Photo by Aristide Economopoulos/NJ Monitor)
Concealed carry licenses in Washington jump after approval of gun permit law

The number of Washingtonians licensed to carry concealed pistols is climbing rapidly… Continue reading

Judge John Coughenour. (Photo provided by U.S. District Court for the Western District of Washington)
‘It’s just so disgusting’: Judges in WA detail threats after Trump-related rulings

After Judge John Coughenour ruled against the Trump administration, local authorities received… Continue reading

Crews put in stripes on a stretch of express lanes on Interstate 405 in 2015. (Photo courtesy of Washington State Department of Transportation.)
New work zone speed cameras cite 7K drivers in 90 days

Thousands of Washington motorists have been caught speeding through highway work zones… Continue reading

Washington’s food banks are on the brink

Some have already pulled back on what they’re offering, as federal cuts and heightened demand drive deep worries about what comes next.

Amanda Cowan/The Columbian
Congressional candidate Joe Kent debates the issues with U.S. Rep. Marie Gluesenkamp Perez at KATU studios in Portland on Monday night, Oct. 7, 2024.
US Senate confirms Joe Kent to lead a national intelligence agency

Kent lost two consecutive runs to represent southwest Washington in the U.S. House. Sen. Patty Murray slammed him as uniquely unqualified for the job.

Incumbent House members and their opponents have been raising money ahead of the 2026 midterms. (stock photo)
As 2026 midterms loom, Washington’s congressional lawmakers rake in cash

Washington’s most vulnerable Democrat in the U.S. House had a strong fundraising… Continue reading

Gov. Bob Ferguson in a media availability after signing the budget on Tuesday, May 20, 2025. (Photo by Jacquelyn Jimenez Romero/Washington State Standard)
Ferguson’s top policy adviser on extended leave

It’s the latest turbulence for the Washington governor’s senior staff.

Support local journalism

If you value local news, make a gift now to support the trusted journalism you get in The Daily Herald. Donations processed in this system are not tax deductible.