Grape growers in California's Central Valley region have picketed an E&J Gallo winery in protest against the low grape prices being offered by the wine producing giant.

Around 50 growers blocked lorries bringing grapes to the winery for about 30 minutes. The growers say that the $65 per ton Gallo is offering for this year's crop of Thompson grapes, the most common grape grown in the valley, is not sustainable. Gallo and other wineries were offering $75 per ton last year.

The growers maintain that Gallo's size means it effectively controls the price paid by all wineries. But Gallo officials said it was "very minor factor" in the pricing of grapes and that all California growers are facing a severe surplus and reduced demand. "We sympathize with the plight of all California grape growers, but the problem is really beyond our control," said Gallo vice president, Milo Shelly.

According to the Californian Agricultural Statistics Service, the harvest this year will be around 3.3m tons, 8% up on last year. Growers in the Central Valley sometimes sell their grapes for raisin production instead but raisin prices are also at a record low. Last week, the East Side Winery, a co-operative in Lodi was sold off, with management citing the glut and resulting low prices as the reason for the company going out of business.