(MercuryNews) - A small-time vintner's use of volunteer workers has put him out of business after the state squeezed him like a late-summer grape for $115,000 in fines -- and sent a chill through the wine industry.

The volunteers, some of them learning to make wine while helping out, were illegally unpaid laborers, and Westover Winery should have been paying them and paying worker taxes, the state Department of Industrial Relations said.

"I didn't know it was illegal to use volunteers at a winery; it's a common practice," said winery owner Bill Smyth.

State law prohibits for-profit businesses from using volunteers.

Before the fine, volunteer labor was common at wineries in the nearby Livermore Valley, said Fenestra Winery owner Lanny Replogle.

"But not anymore," he said Monday. When word got around, several wineries sent their volunteers home.

Westover was cited in July for not paying minimum wage, not providing wage statements and not paying workers' compensation insurance, said Peter Melton, a spokesman for the state.

"These are not idle things. People should be paid for their labor. The workers' compensation violations are very serious. What happens if someone has a catastrophic injury at the winery?" he asked.

And, he added, "It isn't fair to wineries that are paying their employees to have to compete against for-profit wineries that do not."