That’s a jump from chemicals found at about 75 percent of illegal growing operations discovered on public land last year, and it’s six times as high as in 2012.

Federal and state officials launched a summer-long crackdown driven in part by new concern over the increase in the use of the highly toxic pesticide carbofuran.

Researcher Mourad Gabriel, one of the few researchers studying the ecological impact of illicit grow sites, said the pesticide is so powerful that a quarter-teaspoon can kill a 300-pound bear.

He and fellow researchers at the Integral Ecology Research Center in northwestern California found 89 percent of sites this year have been confirmed or are strongly suspected to be contaminated with what he called “highly deadly toxic chemicals.”

The crackdown aided by $2.5 million in federal money led to 95 growing sites and the removal of more than 10 tons of fertilizer, pesticides and chemicals.

U.S. Attorney McGregor Scott said federal authorities are concentrating their efforts on hazardous illegal grows on public land instead of targeting California’s new recreational marijuana industry.

“This isn’t about the marijuana, it’s about the damage that’s being done,” he said in an interview before a news conference to announce the findings. “What is happening here is illegal under anybody’s law.”

California Attorney General Xavier Becerra, who leads the nation’s largest marijuana eradication program, said state drug agents last week found gallons of carbofuran being added to irrigation water at an illegal site in northwestern California. The water ultimately makes it into the water supply in a rugged, mountainous area near the city of Redding.

Investigators suspect some illegal grows are now being moved into agricultural areas where they blend in alongside legitimate marijuana and other crops. For example, they raided two illegal marijuana farms south of Sacramento this summer based on information on a cellphone found at an illegal grow in the Mendocino National Forest last year, Scott said.

“Because of the legalization, our operating theory is that it’s a whole lot easier to go set up a greenhouse in the valley somewhere than it to have to pack all of this stuff into the national forest,” he said in the interview.

The pot is mostly headed out of state and could not pass California’s stringent standards for legal weed because traces of the toxic chemicals are often found in the plants, officials said.

U.S. Forest Service Chief Forester Vicki Christiansen estimated that 1.2 billion gallons of scarce water are diverted to illicit grows in California national forests each year. And

California is not alone, with illegal drug traffickers found in 72 national forests in 21 states, she said, calling it “a major national problem.”

Authorities seized nearly 640,000 plants, more than 25,000 pounds of processed pot, more than 80 firearms, $225,000 in cash and made nearly 80 arrests in California. They hauled out nearly 60 tons of trash, including nearly 84 miles of irrigation hose.

Work crews cleaned up 160 toxic sites, but have a waiting list of 830 contaminated sites, some found eight years ago and still awaiting their turn.

Part of the problem is the lethal pesticides pose a danger to cleanup crews, Scott said in the interview.

“If they go in and there’s a certain level of toxicity, they just have to back away and then let time go by before they can safely go in and try to do the reclamation,” he said.

Failures have been triggered by inaccurate labeling or contamination from pesticides, bacteria or processing chemicals.

Those testing requirements and results have left some retailers with severely limited inventory over the past few weeks, as cultivators and product manufacturers scramble to get compliant products to market.

There was a big gap at the beginning of the month with the supply of marijuana buds in particular, according to Nick Rinella, chief operating officer of Verdant Distribution, a Long Beach-based independent cannabis distributor.

The new testing requirements have also created backlogs at busy labs.

The state has licensed just 31 testing labs, most located in Northern California, and many of them aren’t yet taking customers. As a result, Rinella said cannabis safety tests are taking between one and two weeks.

And this week the first cannabis product was recalled from store shelves because it doesn’t meet new standards regarding pesticide levels.

While that’s concerning, in the short term, industry experts believe it’s also a sign that California’s cannabis industry is maturing and starting to look like other regulated markets, such as alcohol and food.

Wrong labels

California launched legal recreational marijuana sales and imposed new rules for the cannabis industry on New Years Day. But state regulators gave businesses a six-month grace period to comply with some rules, including a requirement that they could only sell products that had been tested for safety by a licensed lab.

That grace period ended July 1, and the state says since then labs have tested 5,268 batches of marijuana, about 20 percent of which failed to meet state standards.

Those numbers would likely be higher if companies weren’t paying for independent lab tests before putting their products through the official supply chain, according to Verdant Distribution founder Brian Blatz.

“Smart brands are pretesting first, then testing again in the labs,” he said.

More than two thirds (68 percent) of the cannabis batches that failed in state tests did so because of inaccurate claims on the labels. Specifically, labels often over-state the amount of THC — the compound in cannabis that makes people feel high — that’s actually in the cannabis, according to Bureau of Cannabis Control spokesman Alex Traverso.

While that’s not necessarily a safety hazard, it can lead consumers to overpay for products that aren’t as strong as advertised.

Pesticides trigger recall

Nearly one in five of the failed tests (19 percent) were related to pesticides. In some cases, the cannabis tested for traces of pesticides that are totally forbidden; in others, it tested with higher levels of pesticides than the amount deemed safe by state law.

Los Angeles-based company The Bloom Brand announced Wednesday it was recalling four vaporizer cartridges with cannabis oil that doesn’t meet state standards for safe levels of the pesticide Myclobutanil.The fungicide is commonly used on food crops, such as grapes and almonds, but is believed to be unsafe when heated — a process that’s common for marijuana smokers.

The Bloom Brand cartridges were sold to 100 stores throughout the state between July 1-19. It’s not yet clear how the products got to market after July 1 with unsafe levels of Myclobutanil.

“We are working closely with (state cannabis officials) to remedy this issue and expect clean, compliant products to be back on shelves in three weeks,” the company said in a press release.

Some marijuana is testing positive for pesticides that cultivators never used, according to Micah Anderson, president of the Southern California Responsible Growers Council, a cannabis trade group. He said product from several growers who’ve taken over former vineyards, for example, failed initial tests because the soil was contaminated, with stricter limits on pesticides allowed in marijuana than in wine.

“For growers, this will definitively be the biggest challenge they face,” said Cliff Yeh, co-founder of Encore Labs, a cannabis testing center in Pasadena.

There are 60-plus banned or regulated pesticides. Growers can pass the majority of the limits on the pesticide guidelines, Yeh said, but if they fail on a few the whole batch is considered a failure.

Other contaminants

Around 6 percent of lab test failures since July 1 have been due to microbial impurities, such as mold and bacteria. The most common microbes showing up are the fungus aspergillus and the bacteria e.coli and salmonella, all of which can develop in marijuana if it isn’t properly stored with careful controls for humidity.

Another 5 percent of failed marijuana samples have involved concentrated waxes and oils that tested positive for residual solvents, such as ethanol, butane and isopropanol. Those chemicals are used to extract THC and other active ingredients from marijuana plants.

Some additional marijuana testing requirements will be phased in Dec. 31.

Starting in 2019, all marijuana products will need to be tested for heavy metals and mycotoxins, toxic substances that can come from mold. Products will also need to be tested for levels of terpenoids, the organic chemicals that give marijuana its distinct aroma and play a role in its effects. And marijuana-infused edibles will have to be tested for moisture content, to make sure they’re not breeding grounds for bacteria and mold.

And more as yet unspecified adjustments are expected, with the state still crafting permanent industry regulations. But just three weeks after the latest testing requirements took affect, Rinella said shelves at marijuana shops are starting to fill back up with product deemed safe for consumers.

Profit margins for most licensed cannabis companies remain thin as they struggle to make it through turbulence that comes when a gray market is fully legalized, Blatz said. But the producers that do survive are competing to see who will be the first Anheuser-Busch of cannabis.

“Because the market is still maturing, there’s not really brand loyalty yet,” he said. “But it’s coming.”