General Electric Co. announced yesterday that it will stop producing its own microwave ovens, forcing it to lay off half its 1,800 employes at its Columbia, Md., plant.

GE said that although it will continue to sell microwave ovens under its own name, they will be made by other manufacturers -- presumably foreign suppliers.

As a result, GE will lay off 545 employes this September when the Columbia plant -- the only one making GE ovens in the United States -- stops producing over-the-range microwave ovens. Another 355 employes will be laid off in mid-1986 when the company stops producing countertop ovens.

The plant will continue to make electric ranges and ovens and will serve as the major Northeast distribution center for all GE major appliances.

"We're very sad about what's going to happen," said Harvey Caras, manager of employe and community relations at the Columbia plant.

He noted, however, that the decision to stop production was in keeping with GE's new corporate policy to stop manufacturing products where the company does not have a major share of the market.

"There are at least 50 different suppliers of microwave ovens in the U.S.," Caras said. "It is a highly competitive market where we don't have a major share, as we do in the sale of refrigerators or electric ranges. . . . We made a tough business decision and decided that instead of putting our money into researching, developing and manufacturing microwave ovens, we should invest our resources where we feel we have a better shot of winning."

Caras said the company will continue to sell microwave ovens under the GE and Hotpoint brand names. But the ovens will be made by manufacturers under contract to GE. Caras said this will enable GE to keep up with technological advances without having to bear the costs of research and development.

"It certainly is a strong possibility" that most of these models will be produced by foreign manufacturers, Caras added.

GE will continue selling microwave ovens, Caras said, because it wants to continue providing a full line of major kitchen appliances. "We have to have the microwave in that line," he said.

GE is one of the largest employers in Howard County, said Manus O'Donnell, director of the county's department of citizen services. The layoffs will reduce the number of jobs there by about 2 percent. " O'Donnell said he is hopeful that many workers will be retrained by GE for new jobs before the layoffs begin.