San Francisco — Helicopter pilots are once again spraying pesticide over areas of Alameda, San Mateo, and Santa Clara Counties in California's two-year war on the Mediterranean fruit fly.
That may seem a strange way to begin describing the campaign for the US Senate seat being vacated next year by Republican S.I. Hayakawa. But the fact is that if the Medfly survives this spring's attempt at eradication in California, Gov. Edmund G. Brown Jr.'s chances to become a US senator in 1983 could be wiped out.
No one expects Governor Brown to have much difficulty winning the Democratic nomination over a gaggle of lesser candidates in California's June 8 primary. But public perception of Brown's stewardship in Sacramento for the past eight years has become linked to his handling of the Medfly problem.
While Brown is almost certain to campaign in the general election as much against ''Reaganomics'' as against his GOP opponent, the tenacious fruit fly could become a powerful symbol of what his Republican adversaries claim is an unimpressive record as governor.
The primary campaign seems to have lasted at least as long as the Medfly crisis - which began July 5, 1980. As the race enters its final two months, a California Poll indicates that on the Republican side it has become practically a two-man contest. US Rep. Barry Goldwater Jr. of Los Angeles maintains the top position he's held since entering the race last summer. But San Diego Mayor Pete Wilson has narrowed the gap between first and second to a mere 5 points. In a January poll Wilson was tied for second with US Rep. Paul (Pete) McCloskey of Menlo Park, 16 points behind Mr. Goldwater.
Maureen Reagan, the President's daughter, is hanging onto fourth place in the latest poll. The only woman in the Senate race in either party primary, she gained one point, from 9 to 10, between the January and March samplings. But observers see no sign that her candidacy will suddenly come alive.
Arch-conservative US Rep. Robert Dornan of Los Angeles leads the bottom four in the GOP field, supported by 5 percent of those sampled by Mervin D. Field's nonpartisan public opinion survey.
Pollster Field points out how support for the top three GOP candidates ''masks two wholly different patterns of support within southern and northern California.'' He says that in the north - which contains about 40 percent of the state's Republicans - McCloskey gets a 35 percent rating, Goldwater 25, and Wilson 17. But in the south, where some 60 percent of Republican voters live, Goldwater gets 32 percent, Wilson 28, and McCloskey 7.
Sprawling, populous, and complex, California is, in the political realm, a classic media state. As election day approaches and the GOP contest tightens, it is quite likely that the plurality needed for the Republican senatorial nomination will be won through the use of television. That takes money - a lot of it.
Goldwater, whose low-key campaign seems to have handed momentum to Wilson, received considerable funds - at least some of them from outside the state - through direct-mail solicitation. A campaign spokesman says that much of that money has been saved for the late-stage media campaign, and some $250,000 already is committed for TV commercials in May.
Wilson, who some say bought his recent California Poll gains with heavy TV spending, is said by his manager to have some $200,000 still in the bank. He probably will attract more - especially with the apparent backing of President Reagan and the enthusiastic endorsement of the President's brother, Neal.
McCloskey admits that without some gains in southern California he can't hope to win. Ron Smith, manager of the congressman's southern California campaign, says that despite the discouraging poll figures, McCloskey expects increased support from voters in the region, based on their perception that he is the Republican most likely to defeat Brown in November. Already, he says, southern California contributions to McCloskey's campaign are increasing. The congressman expects to have some $1 million to spend in the big May TV push.
Mickey Kantor, Brown's campaign manager, happily admits that his candidate is ''sitting pretty.'' Despite a low job-performance rating in a January California poll - 23 percent excellent to good, 33 fair, 41 poor to very poor - Brown gained 6 points, from 51 percent to 57, between the January and March voter samplings on the Democratic Senate race. Novelist Gore Vidal, a last-minute entry, quickly took second place with 10 percent. Three others trailed.
California Senate preferences
Republicans March 1982 January 1982 Goldwater 29% 34% Wilson 24 18 McCloskey 18 18 Reagan 10 9 Dorman 5 6 Others/Undecided 14 15 Democrats March 1982 January 1982 Brown 57% 51% Vidal 10 - StateSen. Paul Carpenter 8 13 Fresno Mayor Daniel Whitehurst 8 9 Others/Undecided 17 27 Source: The California Poll Also of note from California
* Although Lt. Gov. Mike Curb narrowly missed getting the endorsement of the California Republican Assembly--an anointment of value in securing votes on the far-right Republican fringe, he staged a surprising comeback against his rival for the GOP gubernatorial nomination, state Attorney General George Deukmejian, in a recent California Poll. Mr. Curb leaped from a 32-to-43 disadvantage to a 50-to-40 lead.
* California conservationists apparently won a significant battle last week. The Reagan administration quietly restored President Carter's bans against oil and gas drilling in certain areas off the California coast. US Interior Secretary James Watt had earlier obtained suspension of the prohibition against exploration in the Point Reyes and Farallon Island sanctuary near San Francisco and the Channel Islands sanctuary off Santa Barbara. Environmentalists point out , however, Mr. Watt's five-year oil lease plan could still affect some 37 million acres off the coast.
* California Supreme Court Chief Justice Rose Bird, probably Governor Brown's most controversial appointee, is under attack again. Conservative state Sen. H.L. Richardson (R) announced that $400,000 will be spent in a drive to force a recall election aimed at ousting Chief Justice Bird. Conservative critics charge her with being soft on crime, among other things. Earlier, the state Republican Party considered but decided against a Bird recall drive this year.
Governor Brown signed two firearms laws that will be added to California's arsenal of new anticrime measures. One makes a jail term mandatory for anyone previously convicted of certain serious crimes who is caught in possession of a loaded or concealable gun. The other imposes stiffer penalties against persons convicted of using guns to assault policemen or firemen.