California is struggling to eradicate bigger, more destructive marijuana farms on public lands there, reports the Los Angeles Times. Pot cultivated on public lands surged in the last decade, a side effect of the medical cannabis boom. In 2001, several hundred thousand plants were seized in the state. By 2010, authorities pulled up a record 7.4 million plants, mostly on public land. (USA Today reports the activity has now spread to 20 states and 67 national forests.)

Law enforcers long have targeted these operations as "cartel grows," with the hope of working from the busts in the forest up the drug hierarchy, maybe all the way to the Sinaloa Cartel or the Zetas. But after years of raids and work with informants and wiretaps, agents realize the operations seemed to be run by independent groups of Mexican nationals, often using undocumented fieldworkers from their home regions. Officials now say it appears no major cartels are involved.