A decade of dramatic growth in theaters and audiences is being jeopardized by the need for nonprofit professional companies to raise ticket prices to survive.

"It is ludicrous to talk about accessibility to the theater" when companies may have to price their tickets beyond the financial reach of many potential theater-goers, Donald Schoenbaum, managing director of the Guthrie Theater in Minneapolis, told a meeting of the National Council on the Arts here yesterday.

Schoenbaum was among members of the National Arts Endowment theater advisory panel asking the Council to approve a 20 percent increase in theater grants next fiscal year to $7.4 million.

The warning about prohibitive theater prices came as a recent survey showed a spurt in theater activity over the last 12 years - resident professional companies rose from 15 to 70 and development theaters from 10 to 200.

Zelda Fichandler, Arena Stage's founder the producing director, told the council that she remembered starting in 1950 with pretensions to art and no money. "Today, some 240 productions and 28 years later, it's just about the same," she observed.

Both Schoenbaum and Fischandler emphasized that theaters now are earning 65 percent of their way at the box office and are playing to 80 to 100 percent capacity. Since attendance can't be increased dramatically to pick up the budget slack, higher priced tickets are the only way to increase earned revenue.

If budgets are cut down, they added, there will be fewer performances and less adventurous drama as companies have to depend on "bread and butter" plays.

"The challange of the next few years will be maintaining quality," Schoenbaum said.

Fischandler cited Thoreau's advice, not to increase wants but to decrease needs, and hoped that theaters would not have to operate on that philosophy.

Another quotation came from Arthur Ballet, professor of theater arts at the University of Minnesota and cochairman of the theater panel, who made a particular plea for funds for experimental theaters.

He recalled Pablo Picasso's observation: "God is really only another artist. He invented the giraffe, the elephant and the camel. He has no real style. Like all of us, he just goes on trying other things."