Efforts renewed to put marijuana growers out of business.

The appearance of law-enforcement helicopters is one of the surest signs of fall in this remote redwood country, where breathtaking scenery serves as a cover for the nation's largest marijuana crop.

And autumn is literally in the air here as chopper traffic increases for the annual marijuana harvest that lasts from August to October. The county district attorney calls this period the ''fall follies,'' as politicians, press, and nearly every government agency, from local sheriffs to the Federal Bureau of Investigation, descend on the rugged terrain.

Law-enforcement agents, armed with shotguns and sanvicks (straight sticks with a cutting blade on the end), try to chop and burn as many of the plants as possible before the planters can market the crop of sensimilla. Sensimilla, which means ''without seeds'' in Spanish, is a California hybrid of marijuana that is the most potent, expensive, and sought-after form in the world.

Campaign Against Marijuana Planting is a 70-agency effort aimed at eradicating California's marijuana crop. CAMP, the nation's biggest single effort to combat marijuana, receives more than a third of the $3.3 million the Drug Enforcement Administration uses to fight domestic marijuana cultivation in 44 states.

CAMP ''has been a model for other countries, to demonstrate that we are sincere in our eradication efforts,'' explains Bill Ruzzamenti, a federal Drug Enforcement Administration (DEA) official assigned to CAMP as deputy commander. ''Cultivation of marijuana was one of our lowest priorities,'' he admits. ''We never wanted to believe there was a domestic marijuana cultivation problem.''

But the DEA estimates that domestic production accounts for 11 percent of the marijuana consumed in the United States. Marijuana-growing here, which started as a backyard enterprise, has become a sophisticated business worth $1.5 billion , by some accounts.

More than 50 percent of the marijuana grown in northern California is found on remote public lands webbed with irrigation tubes that feed water through individual spigots to hundreds of marijuana plants in hundreds of ''gardens.''

Early one morning recently, this reporter joined raiders to hike along a ridge on US Bureau of Land Management acreage in this forested county, some 200 miles north of San Francisco. The nearest town is Garberville. Scattered in the woods was one crop of 2,000 plants. Potting soil, fertilizer, and tools were stockpiled next to an automated irrigation system.

Part of the reason marijuana-growing flourished here is that the federal government has emphasized halting marijuana imports and has not rigorously enforced domestic-cultivation laws.

Meanwhile, the generation that came to the isolated northern California counties to ''get back to nature'' found that its backyard experimentation - the development of sensimilla - created a demand too heavy for a cottage industry to meet. Today, the marijuana harvest is so big here that it's regarded as a mainstay of the local economy.

Worth about $2,000 a pound on the street, the marijuana here is closely guarded. Booby traps - laid by wary growers to prevent poachers, hikers, or hunters from wandering among the plants - threaten those who wander through these rural areas.

''The old perception was (that) the grower of marijuana was a counterculture misfit, but we're finding more and more (growers) are convicted felons,'' explains Mr. Ruzzamenti of the DEA. He says a sense of lawlessness exists here and notes that, though not directly connected to drug dealing, 18 murders were committed in Humboldt County in 1982 and 1983. Three a year is considered to be the ''normal'' homicide rate.

''A few years back it was the feeling of the populace that this (marijuana) somehow would be a boon to the local economy,'' he says.

Locals, too, tell stories about residents who pay cash for $10,000 automobiles and live in nice homes without a visible means of income. Many are fond of the changes brought by the ''alternative lifestyle'' of some of the hippies who came here in the early '70s. One merchant says the foreign movie theater, the bookstore, and two arts festivals here comprise a culture that wouldn't exist without the money or worldly tastes of the ''growers.'' But the community is also aware that the illegal activity has brought disruption, negative publicity, and the intrusion of law-enforcement officials.

Although the CAMP program has grown from 14 counties in 1983 to 37 counties this year, officials admit they don't have the resources to destroy all the marijuana they've identified from aerial scouting. And the $1.9 million spent on the program is merely a fraction of the overall $340 million DEA budget. So, with an estimated 20 million American marijuana smokers who create a demand for the domestic crop, how deep a dent can CAMP put in the extent of marijuana use and sales in the US?

Jay Nickerson, assistant to the director of the National Organization for the Reform of Marijuana Laws, says: ''Marijuana cultivation is a product of economic forces. When there's a demand for a product, somebody is going to provide it, and the profits to be made in this are outrageous.'' He says legalization would put controls on marijuana that would begin to limit its availability to children , regulate the purity and safety of the drug, produce $13 billion in tax revenue , reduce inflated black-market prices, and clean up the lawless element in places like Humboldt County, where illegal trade fosters an atmosphere of siege between the law and the growers.

But the DEA's Ruzzamenti says these are arguments that have been used to rationalize the legalization of almost any drug, including alcohol. ''Marijuana is illegal,'' he says, because a majority of Americans have not seen fit to make it legal.

Indeed, CAMP has increased growers' perception of the risks involved. Growers are ''going to indoor cultivation and smaller plots'' as a result of CAMP, says Tom Byrne, chief of the cannibis investigation section of the DEA. ''We're putting heat on growers,'' he says.

Prosecutors in the CAMP program - the state attorney general and the US attorney - have made marijuana growing even less desirable by pushing for prosecutions under tax laws rather than the relatively lax laws for marijuana cultivation. They are pushing asset forfeiture, which allows the government to seize land, equipment, cars, and any assets acquired with the proceeds of illegal cultivation.