The Reagan administration has run into widespread citizen protests in its effort to curb marijuana use by spraying pot fields in national forests with the toxic herbicide paraquat.

Current opposition, however, is coming not so much from marijuana smokers, but from ministers, farmers and local government leaders.

A group of Georgians calling themselves Citizens Against Paraquat Spraying (CAPS) recently won a federal court order to halt the spraying in their state after federal agents kicked off the paraquat campaign there on Aug. 12.

Their protest drew national attention and similar groups are organizing in Kentucky, Tennessee, South Carolina, Florida and elsewhere. Several governors have criticized the spraying, prompting the U.S. Drug Enforcement Administration to announce it will proceed against the states' wishes if necessary.

"We think we do everything conceivable to assure . . . safety," said DEA spokesman Robert Feldkamp. He said agents make sure that a targeted area includes no drinking water supplies and no campers or hikers. The Reagan administration plans to spray marijuana fields in 40 states, he said.

Paraquat, used widely by farmers as a herbicide, can be lethal if inhaled. It became controversial in 1978 when the State Department acknowledged that it was providing it to Mexico for use on marijuana fields there. Mexico is a major source of the marijuana smoked in this country, and many users here feared for their health.

The administration now is trying to persuade Colombia, source of more than three-fourths of the marijuana sold in the United States, to use the herbicide on its pot fields.

The administration filmed the spraying in Georgia to demonstrate to Colombia that it is willing to use the herbicide at home. President Reagan and Attorney General William French Smith also have lobbied Colombian officials on trips to Latin America, DEA officials said.

Feldkamp said the DEA hopes the highly publicized spraying in Georgia will "send a symbolic message" to marijuana growers.

He said agents have recently noticed an increase in marijuana planting on federal lands, such as the Chattahoochee National Forest in Georgia where 70 plants were sprayed. After the Georgia effort, the DEA sprayed about 200 plants in Kentucky's Daniel Boone National Forest, but officials said they do not know when or where they will spray next.

Meanwhile, the Georgians are fuming. Rep. Elliott H. Levitas (D-Ga.) held a news conference to say he has evidence showing the spraying cost more than $16,000 a plant.

DEA officials said they could not provide exact cost figures, but contended that the Georgia operation and one in Kentucky's Daniel Boone National Forest cost a total of between $20,000 and $25,000.

"I still feel the potential physical danger and health risk to the people of Georgia outweighs the importance of making a film clip for the government of Colombia," said Georgia Lt. Gov. Zell Miller, who noted that he lives near the sprayed forest.

Georgia Lt. Gov. Zell Miller and others said residents were not forewarned of the spraying, and many first learned of it when they saw a swarm of helicopters in the sky. The Rev. Jerry Brinegar of the Nacoochee Presbyterian Church in White County, Ga., said 400 people attended a protest meeting at his church two days afterward, followed by a fund-raising hootenanny.

"A lot of people up here think they chose this area thinking we were sparsely populated and backwoods and we'd just take it," Brinegar said. "But people are beginning to wake up and realize how dangerous these toxic substances are."

Brinegar said he has received calls from protest organizers in Kentucky, Tennessee, Florida and South Carolina. In Kentucky, opponents tried but failed to get a federal court order to block the spraying.

Feldkamp said the DEA considered the first two spraying efforts to be successful. In Georgia, agents pulled up the marijuana plants to keep people from coming into contact with them after they were sprayed, making residents wonder why the government went to the trouble of spraying in the first place.

"You could make an argument that the Georgia operation was not cost-effective, but it was a learning experience," Feldkamp said.

In the Kentucky forest, he said, agents staked out the sprayed area for three days to keep people away. It would have taken a team of agents at least that long to cut down the plants by hand, he said.