Moments after he had finished speaking to reporters at the occoquan reservoir in Northern Virginia last week, Lt. Gov. John N. Dalton walked over to an aide's car, picked up an uncerlined copy of a news release and began reading it aloud.

What Dalton, the Republican nominee for governor, was doing is the latest political ritual in Virginia: making a "beeper."

As Dalton spoke, an aide held a microphone attached to a small, battery-powered tape recorder that would be used by his campaign staff to relay his remarks to many of the region's radio stations that did not send reporters to his press conference.

Sure enough, the next morning, as Dalton was out greeting commuters in Reston, his comments on Northern Virginia's water problems were being carried in newscasts by at least one station, Fairfax' WEEL.

But what WEEL news didn't tell its listeners was that John Dalton - not its own news staff - furnished the tape. Under Federal Communications Commission rules, stations are requred to do that, although some campaign aides admit many Virginia stations do not.

In the 10 years since William B. Spong introduced the "beeper" to Virginia during his race for the U.S. Senate, tape recorders have become as commonplace as mimeograph machines in campaign headquarters. Both Dalton and Henry E. Howell, his Democratic opponent, have press aides who specialize in taping such releases and then offering, them via telephone to the state's radio stations.

The tapes are called "beepers" because the FCC used to require broadcasters to have an audible beep on any telephone line from which it would record conversations.

The tapes have gained widespread acceptance among many radio stations that have neither the news staff nor the inclination to send reporters on the campaign trail.

For candidates with little avertising money, "beepers" are generally regarded as one of the most effective and economical ways of getting messages to thousands of voters they might otherwise miss.

That's what made a recent letter from Howell to Virginia broadcasters remarkable. In it, he warned them of their obligation to cover the fall campaign. Frank Bolling. Howell's press secretary, who drafted the controversial letter, was quick to say that he didn't think the hostile reception it received from broadcasters would impede the use of Howell-furnished "beepers."

Dalton's radio specialists, Charles Davis, a former Richmond radio reporter, however, saw the flap over the Howell letter quite differently. It was, he said, an overreaction by Howell to the wide acceptance Dalton's "beepers" have had around the state.

Bolling denies that, saying the Howell letter, sent to each of Virginia's 131 radio and television stations, was a sincere effort to encourage them to carry more election news and commentary this year.

Whatever Howell's motive was, the letter does touch on what is an extremely controversial issue in any campaign and one most political consultants advise candidates to avoid: questioning the media.

There was no doubt last week among many Democrats in the state that Howell could have saved himself considerable wrath by having sent the broadcasters a different letter. If he had only offered his and his staff's help to stations in covering the campaign, rather than citing court cases that demand their coverage, his letters would have had a positive impact, some said.

Unlike the national campaigns, where candidates are whisked across the country in chartered jets, state candidates in Virginia tend to bounce from one small airstrip to the next in cramped single-engine Cessnas. The press, if this spring's Democratic primary is an indication will trail along in another small, single-engine plane.

If the candidate is lucky, there may be four or five reporters tailing him at the end of the campaign, all from newspapers. Virginia's broadcast media tend to cover press conferences in big cities, and sometimes little beyond that.

When a candidate is out of the urban areas, in broad stretches of rural Virginia and small cities that can make or break a campaign, the broadcast media tends to be absent. That's what has made the "beeper" so important.

One call to a Charlottesville radio station that operates a 23-station radio news network, and the campaign can get its candidate air time across the state. A few other calls to major stations elsewhere, and the candidate's words can blanket the state.

What's more, since the candidate can carefully rehearse his words before the "beeper" is made, he can avoid sloppy syntax or, what's worse, saying something - as candidates often do - that he will later regret. Radio news directors acknowledge that the "beepers" give candidates a certain degree of control over their news programs. They say their use of "beepers" is no different from a newspaper's use of a candidate's press release.

"We look at it as a sophisticated press release," said Susan Garrett, assistant news director of Charlottesville's Virginia Network, part of radio station WINA.

"If it's newsworthy, we'll consider it," said John B. Tamsey, general manager of Richmond's WRVA. "If it's gook, its gook and goes in the round file."

Some of Howell's supporters last week were wishing that fate had befallen Howell's twopage letter. Even after the Virginia Association of Broadcasters condemned the letter as "an interesting attempt to intimidate broadcasters," Howell offered no regrets for having offered it.

The only mistake he made, he told a Harrisonburg television station, was not to send a similar letter to the state's newspapers. If he does - and Howell has not hesitated to attack the state's media in the past - then the fall campaign could be as controversial for publishers as it has already become for broadcasters.