Hours before dawn, Chuck Clunn stood on a street corner in this dusty border town and shook his head, dismayed at the small number of men milling in the dark. Workers usually swarm streets near the border crossing in the early morning hours, but today Clunn and other labor contractors looking for farmworkers found a crowd half the size they had been hoping for.

"This is usually just people everywhere. Last year the whole town was moving," Clunn said. Now, he said, the foremen say, "Hey, man, we have plenty of generals, but there's no Indians."

For the past year, the fertile valleys here that provide 90 percent of the nation's winter lettuce have faced a labor shortage. The construction industry is booming, luring workers with year-round jobs offering better pay. U.S. Border Patrol agents have been cracking down in nearby Arizona, leading many of those who pick the crops -- almost all of them Mexican and many, by all accounts, illegal aliens -- to avoid the lettuce-growing border counties.

With the lettuce harvest beginning, farmers in the $1 billion winter vegetable industry are panicking about getting their crops out of the ground. Vegetable growers estimate they could be 32,000 workers short of the 54,000 they need for the winter harvest, which runs until March. Last year, local farmers left hundreds of acres of lettuce in the fields because they lacked the manpower to harvest it.

Worker shortages have swept the Western agriculture industry, bringing $300 million in losses to raisin growers in California's San Joaquin Valley in September and causing consternation about this winter's harvest from the Christmas tree farms of Oregon to the melon fields of Arizona.

"Today I have approximately 290 people working in the field," Jon Vessey said recently. Vessey runs an 8,000-acre winter vegetable farm with his son, Jack, near El Centro, Calif. "I should have 400, and for the harvest I need 1,100. . . . There's a disaster coming."

The Western Growers Association, which represents 3,000 farmers, is lobbying the Bush administration to make it easier for farmers to tap the labor pool just below the border.

Labor Department statistics show that about half of the nation's 1.8 million farmworkers are in the country illegally. Tom Nassif, the association's president, said growers try to check workers' documentation but many have falsified papers.

Nassif said a better approach would be for the U.S. government to allow Mexican citizens to live here while working in the fields and return to Mexico when the work is done. His long-term goal is to see passage of the Agricultural Job Opportunity, Benefits and Security Act, or AgJobs. The bill, proposed by Sens. Larry Craig (R-Idaho) and Edward M. Kennedy (D-Mass.), would allow undocumented farmworkers already in the United States to become legal permanent residents and would streamline the current guest-worker program.

"There are just some jobs people don't want to do," Nassif said. "It's the most developed nation in the world using a foreign workforce, and people need to recognize that. We need to make them legal."

Jack Vessey said he listed openings for 300 laborers at the state office of employment last week to prepare the lettuce fields for harvest. "We got one person," he said. "He showed up and said, 'I'm not going to do that.' "

Marc Grossman of the United Farm Workers acknowledged that the growers face a labor shortage, and he said his organization is cooperating with Western Growers to back the AgJobs bill. But Grossman said the labor shortage "is largely of their own making."

In the fields, he said, "the pay is so low, the benefits nonexistent, the conditions so harsh, if you can, you do something else," Grossman said. "You save money and buy a tool belt and go into construction. Or you work at a hotel. Anything to escape the fields."

Growers and workers also said illegal workers have moved north because of increased enforcement of immigration laws along the Arizona and eastern California border with Mexico. Border Patrol arrests were up 41 percent between fiscal 2005 and 2004 near Yuma, Ariz., where lettuce is grown.

Workers and labor contractors have numerous stories about the Border Patrol targeting farmworkers.

"Over in Brawley I lost three crews to the Border Patrol," said Gilberto Lopez, a labor contractor who competes with Clunn to provide workers to local farms. "People hear about that and leave. They don't want to be harassed."

Border Patrol officials denied focusing on farmworkers.

"Our position is not to target agricultural workers specifically," said Michael Gramley, spokesman for the U.S. Border Patrol's Yuma sector. "Our target is any illegal aliens."

Yuma Mayor Larry Nelson, a Republican, said he once believed the border should be closed entirely. Responsibility for his community's economic health has changed his mind, he said.

"We have more jobs in America than we have workers," he said. "If you took every illegal out of the United States right now, you would shut down the food industry, the vast majority of the hotels and all the service industries. If you stop [immigration], this nation will come to a screeching halt."

Jon Vessey agreed. "Most people out there say, 'Let's close the borders. And then we'll just go down to Von's and get our vegetables,' " he said, referring to a supermarket chain. "Well, it doesn't work that way."

Farmworkers cross back into Mexico after working in San Luis, Ariz. Growers say they could be 32,000 short of those needed this winter.Ricardo Gracia, left, runs a bucket of vegetables to a trailer where he will collect plastic chips, each redeemable for a 20-cent increase over the minimum hourly wage.