For three years now, Tommie Willis has been hiring the same two Mexicans to work on his tobacco farm here in Southside Virginia. They arrive in April, when the young plants are transferred from planting beds into the fields, and stay until October, when the leaves are cured in the high, narrow barns that dot the local countryside.

Willis calls the Mexicans his "insurance." Without them and the controversial program that brings them here on temporary visas each year, he says he would be back out driving around Pittsylvania County every morning, rounding up local workers who had promised to take the jobs.

"That was all I'd have, was promises," says Willis. "You don't have workers when you need them unless you get Mexicans."

Other Southside farmers agree, which is why since 1980 they have imported between 1,200 and 1,500 legal foreign workers--virtually all Mexicans--into the tobacco fields each year, filling about one-fourth of the available jobs.These jobs were traditionally filled by poor sharecroppers, most of them black, whose children have since shunned what has been described as the nastiest and most poorly paid of agricultural stoop labor.

Virginia is the only state in the South using legal foreign labor in tobacco fields (foreigners have been hired for years in Virginia apple orchards), but some say the practice may spread if restrictions on the federal "guest worker" program are relaxed under an immigration bill now pending in Congress.

That prospect alarms labor groups that say that the "guest worker" program, which now brings in an estimated 20,000 foreign sugar cane cutters, apple pickers and other agricultural workers nation-wide, is already abused. Complaints have been filed, here and in other states, charging growers with overlooking, even discouraging, American applicants in their eagerness to make room for the foreigners.

Critics of the program say it puts American workers at an unfair disadvantage, even though the law requires that both groups receive the same wage, which in Virginia is set at $3.81 an hour, 45 cents above the minimum wage.

While farmers say their foreign workers are reliable, the critics call them captives, forced by the terms of their visas--known as H2 in bureaucratic parlance--to do whatever is asked of them. Brought into this country to work for a specific employer for a specific period of time, the foreigners can't and don't wander off the farm, according to spokesmen for migrant aid groups.

"With H2 workers, you end up with a closed labor force," said Kevin Boyd, director of the Migrant and Seasonal Farmworkers Association in Richmond. "If you're a Mexican national, you"ll accept anything and will not complain. If you don't work, you have no right to be here. If you complain, that's it."

Resentment of the tobacco farmers' hiring practices has been simmering for a long time in Southside Virginia, but this year the controversy has caused reverberations as far away as Florida and Texas, where migrant aid groups are up in arms over what they say is evidence of unfair treament of domestic laborers by the Virginia growers.

To qualify for the H2 program, employers are required to advertise their jobs in areas with high unemployment. This year, at the prodding of the U.S. Department of Labor, the Virginia growers went to Florida to recruit among the large pool of unemployed Haitian refugees who have working status in this country because of special rights conferred to them in 1980.

The recruiting efforts of the Virginia Agricultural Growers Association, which represents 210 farmers in 10 counties and is one of the two groups in Southside that hires Mexicans, ended in disaster for all involved. The 43 Haitians, who came here expecting jobs, were told when they got off the bus that they couldn't work together, not even in pairs. Eighteen of them demanded to return to Florida immediately. Their anger and confusion provoked what the local papers described as a "near riot," although some who were present said the only disturbance occured when a Haitian woman, told she couldn't work with her common-law husband, let loose a stream of invective.

By last Friday, all but six of the Haitians had left Virginia, most of them complaining of the loneliness of working one to a farm. Their exodus, and the reaction of the growers to their complaints, has been cited as evidence that the Virginia growers were never serious about hiring domestic workers in the first place.

In particular, migrant groups note that no effort was made to allow the Haitians to work together, even though in many cases they were joined on the farms several days later by two or more Mexicans.

"It would be seem sensible to pair them up, so they could talk to each other," said Boyd. "If I was Haitian, stuck out in a rural area with no one to talk to, I'd leave, too. I have a suspicion that it was done for that reason, that they woud refuse the job."

The growers, who have registered their own complaints through Rep. Dan Daniel (D-Va.) about the U.S. Department of Labor's unreasonable demands, make no apology for the working conditions offered the Haitians. They say the workers had been warned in Florida that they would be scattered, although no one could predict to what extent.

"I don't make it easier for anyone," said Curtis Rowland, executive secretary of VAGA. "If they can't accept my terms of employment, what am I supposed to do?"

Added Al Misler, a Washington attorney who represents the growers assocation: "This isn't a social affair where they are going to dance together. People don't operate farms that way."

As the Haitians slowly made their way back to Florida, complaints began to surface about the growers' hiring practics.

In Texas, migrants' attorneys have pounced on what they say is evidence that the Virginia group, through an intermediary, advanced transportation money to Mexican nationals, while refusing to do the same for American workers. The H2 program requires that employers offer Americans and foreigners the same package.

Spokesmen for VAGA emphatically deny that they have ever advanced transportation money to Mexicans. The letter, sent out by an independent company under contract to the growers, was unauthorized, they say.

But the charge is now being investigated by the Labor Department, the Texas employment service and a Texas congressman.

At the urging of the Texas Rural Legal Aid Fund in Laredo, the Virginia jobs have been circulated among local Texas employment agencies, but so far, with little success. A recent breakdown showed that of the 360 domestic workers called in to apply for the tobacco jobs, half failed to show for interviews and another 99 rejected the work out of hand, many because of the lack of transportation money, according to Texas employment authorities.

That response, the growers say, duplicates a pattern seen elsewhere and only provides further evidence that American workers no longer want to work in tobacco. Last year in Virginia, VAGA received applications from 267 local applicants for tobacco jobs; of those, half never showed for interviews. Only 33 were ever hired, and few of those lasted the grueling five-month season.

"Due to the very lenient welfare system, no one will accept employment in agriculture any more. It seems to be degrading," said Rowland. The only reason North Carolina and other tobacco states manage without H2 workers, he says, is because they use illegal aliens.

Local activists such as black community leader Cora Tucker in South Boston, however, charge that Virginia farmers resist hiring local people because they have failed to adapt to the changing economic realities of American farmwork.

"People are upset when they are out of work and see Mexicans riding on the back of trucks off farms where they used to work a few years ago," said Tucker. "It creates a bad feeling." If the proposed Simpson-Mazzoli bill, a major overhaul of a wide range of immigration laws, is enacted by Congress in its present form, farmers will have an even easier time hiring guest workers. The bill, as passed last week by the Senate, would relax some of the programs' requirements, partly to allow growers who have relied on illegal aliens to shift more easily to the legal program.

Those restrictions, including the requirement that growers look beyond their own states for domestic workers, may be restored in the House, as they were last year.

In the meantime, VAGA is applying for another 599 Mexican workers in July when the tobacco season gets in full swing, to join the 264 who have arrived already.

Willis, one of the few farmers who still employs a Haitian in Southside Virginia, hasn't applied for any more Mexican workers, beyond the two who work for him now. Down the road, Irye Crowder, who is also working two Mexicans and a Haitian, says he may hire one or two more Mexicans, depending on whether Joseph St. Hubert stays the season.

St. Hubert, who speaks a little English, wants to keep the job. "In Florida, plenty Haitians and no jobs," said the 40-year-old Haitian, who sends money back to his wife and two children in Port-au-Prince. "No job, no money, no take care of babies."

Crowder, a veteran farmer who believes in treating his workers "like people, not like nobody's dog," hopes the man from "Haitia," as he calls it, stays and that he can find available local workers.

"Nobody would want Mexicans if they could get local help. It wouldn't make any sense," he said.