When members of Congress and labor leaders ask Harry Kubo why Fresno growers need more Mexican laborers to pick their raisins and strawberries, when they ask why can't he use the thousands of unemployed workers already here, he tells this story:

One day last summer a member of the Nisei Farmers League, the growers group of which Kubo is president, asked if he could find 30 workers to pick 20 acres of grapes for raisins when they ripened in a month. Kubo called Doreen Caetano, a job developer for a local community of Laotian immigrants, who said it could be done.

"She kept me advised of her progress. She had found nine; she had found 15; by the time the crop was ready she said she had 25 pickers lined up," Kubo said. "She got up at 4 a.m. and went to round them up and found only nine willing to go."

Most lived on welfare and would lose their benefits if they worked more than 100 hours a month.

Time was short. The grapes were reaching their peak. When the small crew arrived at the grower's farm at 6:30 a.m., Kubo anxiously agreed to give them an hour's training and stay with them through the day.

"But when they started to work, most of them did just the opposite of what they were told. When the grower complained they were too slow, they said they would get at least the minimum $3.35 an hour anyway, so why should they speed it up?" Kubo said. A discouraged Caetano, who confirms Kubo's account, took them away that afternoon.

United Farm Workers union leaders in California's Central Valley have little patience with this episode.

"Why didn't he call us to provide some workers?" said UFW first vice president Dolores Huerta, who argues that growers want more foreign workers only to keep wage rates low.

Kubo's group was formed 14 years ago in response to UFW efforts to picket Japanese-American growers, and the mutual distrust continues to this day.

But Kubo's minidrama crystalizes a new debate that has moved from this lush fruit and vegetable growing region to the Congress:

Do the nation's growers need an additional 350,000 accredited Mexican workers each year, and if they do not get them, will the landmark immigration revision bill penalizing them for hiring illegal immigrants have a chance of success?

Kubo decried what he said is a mistaken impression in Washington, D.C., that California growers are all giants with thousands of acres and millions of dollars to get legislation turned their way.

There are some very large ranches in this valley, but the average Fresno area farm is 90 acres, he said. The average for his 1,400-member association -- a majority of whom are white -- is 74 acres. A crop missed because of a labor shortage can wipe out some small operators.

Impressed by these arguments, the Senate has attached to the immigration bill an amendment sponsored by Sen. Pete Wilson (R-Calif.) that would allow as many as 350,000 "guest workers" into the country each year if the attorney general determines they are needed.

From the late 1940s until 1964, U.S. law allowed up to 400,000 bracero workers annually into the country to harvest crops up and down this valley. Charges that growers were providing sub-human working conditions and that braceros were remaining in the United States illegally killed the program.

Mindful of this history, Wilson has added provisions requiring proper working conditions and allowing guest workers to move to other jobs if they are dissatisfied.

To ensure that workers return to Mexico, or whatever country they come from, 20 percent of their gross wages would be withheld until they claimed them at a U.S. consulate back home.

Kubo said he and his growers already pay the prevailing wage for farm labor, about $1 above the $3.35 minimum wage, and those who fear immigrants might be exploited should support the Wilson amendment because it would allow the government to monitor wages.

Having won a narrow 51-to-44 victory in the Senate, the amendment is given only an even chance of surviving in the House.

It is attached to an immigration bill that strengthens the Border Patrol, offers citizenship to illegal aliens who arrived before 1980 and -- most important to growers here -- institutes fines and possible criminal penalties against growers who knowingly hire illegal aliens.

Fred Campbell, who needs 40 pickers to harvest his 80 acres of grapes for raisins, said he would have no choice but to risk the fines if the immigration bill passed with no provision for guest workers.

"If we're short of help, the grapes will just dry up on the vines," he said.

His farm has been in his family since 1919, two generations. Campbell pays his workers $4 an hour and provides them with a shed that includes a refrigerator, stove, beds and a door lock for security.

Each year the same men arrive to pick his harvest and dry the fruit. Campbell said he has advanced some as much as $300 on their anticipated wages and never been cheated.

"We're relying on an illegal work force, that's no secret," Kubo said. He extols the Wilson amendment protections for "the human rights of people coming across the border, whose only desire is survival."

He notes that some growers, including one in his area he once reported to authorities, have housed migrant workers in caves and paid less than the minimum wage.

Critics of the Wilson amendment argue that it will not be needed. Enough illegal immigrants will qualify for amnesty under the immigration bill to meet farm labor needs.

Michael V. Durando, president of the California Grape and Tree Fruit League and a Wilson amendment supporter, argues instead that once illegal aliens qualify for citizenship, they will leave the fields for more lucrative, less physically taxing jobs in the cities.

The unemployment rate among legal resident farm workers is at least 14 percent, and much higher in certain California valley towns. But Tony Vang, executive director of the Lao Family Community Inc. here, said that many of those workers need training and find themselves better off accepting welfare than working long hours for wages just above the legal minimum.

Huerta charged that many workers are paid less than that. Asked about grower complaints that local workers are not as productive as immigrants, she said, "Why should they want to work that hard if they should be making twice as much money?"

Sen. Alan K. Simpson (R-Wyo.), who voted against the Wilson amendment, has complained of the "greed" of fruit and vegetable growers, a charge that turns the sweet-tempered Kubo sour.

"Is it greedy to want to harvest the crop that you've worked all year for?" he said. "Is it greedy to try to survive in our society without any handouts?"