She arrived without warning.

In September 2009, an agent from the U.S. Immigration and Customs Enforcement agency walked through the doors of David's business to let him know he was going to be audited. She wanted to find out if he employed illegal immigrants.

David, who owns a tree nursery in the central San Joaquin Valley, was surprised he had become a target. Among growers, ICE audits are something of a taboo subject, so David hadn't heard much about them in the Valley.

He politely thanked the agent before seeing her off. Then he called his lawyer.

David, who agreed to talk about the audit as long as he was identified only by his first name, is among the growing number of employers in the Valley who are quickly becoming familiar with ICE's renewed focus on audits. In the end, David had to fire one-fourth of his full-time workers because they were in the United States illegally. But he was not fined.

"You have people yelling about how [immigration enforcement agencies] are not doing their job on the border, but up here, they're doing what they're supposed to do," David said. "I don't like it, but they're doing it."

On her first visit, the ICE agent told David he had a week to gather his employees' I-9 forms, which record their Social Security number and immigration information when they are hired. The agent wanted the originals. In early November 2009, she returned with a list of 26 employees whose legal status needed checking.

"The way she put it to me was that I was one of the good employers because I only had a small percentage of workers [who appeared to be illegal immigrants]," David said. "She said that it's usually a much higher percentage."

Acting on the agent's orders, David asked the employees to produce proper immigration documentation. None could.

Reluctantly, David fired them. He had employed many of them for a decade or more and gotten to know them and their children through work, company picnics and softball games.

"They knew why they were fired, but it didn't stop the emotions from occurring," he said. "Some of them really took it hard."

Like most growers, David said he'd rather hire legal workers, but he said there's not enough people willing to work for the low wages he must pay to keep his business competitive.

After firing his workers, David struggled to replace them. But at least the audit came well ahead of the nursery's busy season. A few months later, David was employing another 200 or so seasonal workers besides his full-time employees. An audit then certainly would have disrupted the "harvest," when workers replant the saplings into containers, he said.

"I had gaps in my harvest, which we managed to get through," he said. "But it was a hell of a year for training."

The audit was effective at weeding out illegal immigrants at his business but did little to discourage them from working elsewhere, he said. In fact, within a week all but two had found new jobs.

On his attorney's advice, David signed up for E-Verify, the online government program that helps confirm an employee's immigration status. As soon as the ICE agent found out he had enrolled in the program, she seemed to lose interest, David said.

"She's a pleasant lady," he said. "But I'd rather not hear from her."

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