A federal appeals court yesterday virtually banned the U.S. Forest Service from using the herbicide 2,4-D on its lands in California.

The 9th U.S. Circuit Court of Appeals said that the Forest Service must comply with California pollution laws or get a presidential exemption before spraying.

A moratorium on the use of 2,4-D is in effect in California until new laws regarding its use are written. The Forest Service allegedly decided it couldn't wait for the new regulations and sprayed without a state permit.

The appellate court reversed a decision by U.S. District Court Judge Samuel Conti last Aug. 31 that dismissed lawsuits brought by the Sierra Club and two environmental groups against the Forest Service, several of its officials and Agriculture Secretary John R. Block. Assistant U.S. Attorney Francis Boone said he would confer with the Justice Department and the Forest Service about a possible appeal.

In Riverside, Calif., additional ground water tests were under way yesterday following reports by state health authorities that cancer-causing chemicals were found in 22 private wells near the Stringfellow acid pits.

In Lansing, the state of Michigan ordered Dow Chemical Co. to stop using a hazardous waste landfill at Midland, alleging that the company violated its state landfill permit when hazardous wastes backed up and entered a "clean zone" under the landfill's clay liner.

The order accused Dow of continuing to dispose of hazardous wastes in the landfill after a detection system was contaminated, of failing to take prompt action to repair the landfill and of failing to test for possible ground water contamination.