WEST PALM BEACH, Fla. -- Florida farmers, worried that lawmakers could strip them of their largely undocumented workforce, are warning of an impending crisis in their fields.

Those growers admit that at least 75 percent of their workers are in the U.S. illegally. Most of those workers buy fake Social Security cards and employers generally issue paychecks and deduct payroll taxes and Social Security taxes which they attribute to those false numbers. In that way employers fulfill their legal obligation. They are not obliged to check if the numbers are legitimate.

But a bill now before the Congress, the Legal Workforce Act, sponsored by U.S. Rep. Lamar Smith, R-Texas, would require all employers to use a federal database called E-Verify to check the legitimacy of those numbers and not hire illegal workers.

Smith said his program would "provide growers who want to do the right thing with a reliable source of legal labor" and would also "protect the livelihoods of American workers and the rights of guest workers."

Agricultural interests nationwide and other business groups have opposed Smith's bill, and chances of its passage are questionable.

But Florida farmers are still worried. In Alabama, farmers and tourism industry leaders opposed the adoption of E-Verify there, but it still passed a GOP-controlled legislature and goes into effect April 1. Georgia had previously passed statewide E-Verify, despite opposition by farmers. Many undocumented workers have abandoned both those states, causing losses of crops, according to growers there.

Similar legislation failed in Florida this year but state farmers still fear that E-Verify may eventually be required here. And many fear that what they see as their only alternative, hiring foreigners through a federal guest worker visa program, would carry much higher costs and risks.

A front page article in this month's Florida Grower, published by the Florida Fruit and Vegetable Association, alerts farmers to the legislative dangers and urges them to contact their lawmakers in Tallahassee and Washington.

''E-Verify could create massive disruptions in labor supply," the article says. The publication says there are 1.2 to 1.4 million farmworkers in the United States, with about 75 percent falsely documented. In Florida, there are an estimated 150,000 farmworkers with a similar rate of false documentation, although the rate among purely harvest workers is likely much higher, the article states.

In Georgia, just as in Alabama, it was largely Republican Party lawmakers who went against the interests of farmers, most of whom also traditionally support the GOP. Observers say that illustrates the anger in those states, and across the land, over the number of undocumented immigrants in the country.

''My biggest fear is people are so emotional on this issue and set in their opinion that we are going to have to have significant farm losses before legislators wake up," said Mike Carlton, labor relations director for the FFVA.

''We don't know the consequences of what's happening in Georgia and Alabama and how it will impact labor here in Florida this year. We know farmworkers were avoiding driving through Georgia last year and likely will avoid Alabama. It almost blocks us off."

According to the FFVA, a University of Georgia study of growers of blueberries, blackberries, Vidalia onions, bell peppers, squash, cucumber and watermelon showed that $140 million were lost "at the farm gate" this year due to labor shortages.

When related jobs are added in, such as retail sales and transportation of produce, the state economy lost an estimated $391 million, the FFVA said. "If approximately 75 percent of your work force disappears, what are you to do?" Florida Grower asked.

The publication said the only option growers have is to turn to the federal agricultural guest worker program, known as the H-2A program, which allows the legal importation of temporary farm labor.

But Florida farmers say that program has many problems. The legal guest workers are more expensive than undocumented migrant workers because the federal government insisted they be guaranteed $9.50 per hour, far above the state minimum wage of $7.31. Their transportation must be paid to and from their native country every year and the grower must supply housing.

Carlton said commodities prices are set by what buyers are willing to pay, not by growers, so the difference in cost would likely come out of farmers' pockets and not be passed on to consumers.

Vegetable growers in Florida say another big problem is that importing workers involves considerable paperwork, and glitches with those documents often cause delays in workers arriving.

''Right now the H-2A program creates more problems for many growers than it solves," said Rick Roth, a Belle Glade grower. "It works for growers who have lots of acres and long harvest seasons, like in citrus. But for tomatoes, for example, it doesn't work."

A review of the list of growers who have applied for imported worker visas this year confirmed Roth's assessment. Of 58 growers, 52 are citrus growers and more than 95 percent of the workers requested are for citrus. They total around 6,500.

Carlton said the citrus harvest is months long and those growers can spread the travel and paperwork costs of importing the workers over a longer period, making it cost-effective. But for vegetable growers, the harvest season is a matter of weeks in any one locale and then workers move to other towns and states.

Roth said the H-2A program requires that workers only work for one employer and then go home. Unless vegetable growers in different areas can be allowed to share those workers and divide the costs, the workers will be too expensive, he said.

''They have to stop designing it in a way that people can't use it," Roth said.

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Roth said the government should create guest worker visas that last for several years and allow workers to labor in specific industries for different employers. He also believes that guest worker visas should not be used as paths to citizenship.

Roth said the one argument he would like to stop hearing is that there are Americans citizens who would do the work if wages were high enough.

He said not only is the work back-breaking and hot, but a worker has to pick up and move every few weeks, which most citizens won't do.

''This is a repetitive job for people who don't speak the language," he said. "These people pick the crops for other people who have air-conditioned jobs."

The New York Times contributed to this story.