LOS ANGELES — The largest illegal marijuana bust in Los Angeles County history — which netted 373,000 plants that would ultimately have been worth $1 billion on the street — eradicated only a fraction of the illicit grows in the Southern California high desert, authorities said Wednesday.

The problem is wide-ranging in the Antelope Valley north of Los Angeles, officials said, and has grown tremendously during the coronavirus pandemic. Armed cartel members run massive illegal grows, some spanning dozens of greenhouses, that are detrimental to the state’s legal marijuana market.

Multiple law enforcement agencies carried out a 10-day operation in the Antelope Valley last month that resulted in 131 arrests and the seizure of more than 33,000 pounds (14,969 kilograms) of harvested marijuana plants.

Yet the undertaking only demolished 205 illegal grows out of the 500 seen by aerial surveillance in the area. Last year, Sheriff Alex Villanueva said only 150 illegal grows were identified in the Antelope Valley. Scores more exist in other nearby counties.

The cartel members threaten residents and steal millions of gallons of water amid a severe drought, Villanueva said. The growing operations have poisoned streams and groundwater with harmful pesticides and harmed wildlife and plants.California broadly legalized recreational marijuana sales in January 2018. But the black market is thriving, in part because hefty legal marijuana taxes send consumers looking for better deals.

Officials sought to differentiate between the Antelope Valley operation and the legal market.

“This is not a war on the legal cannabis business in California,” said U.S. Rep. Mike Garcia, who represents the area.