A 10% downgrade in its Californian grape harvest triggered a flurry of concern and share price fluctuations for Australian wine and brewing group Fosters.

The liquor group's Beringer Blass Californian operation downgraded the Self Generating and Regenerating Assets contribution to earnings before interest tax and amortization for the full year to around A$5m, compared with the group's previous estimate of A$23.5m.

The news spooked some investors until Fosters spokeswoman Nicole Devlin said it would have no effect on underlying revenue, cash flow or earnings per share. SGARA recognizes the difference between the actual cost of production and the market value of the group's own grown grape crop.

The share price plunged 3% before rallying and finishing marginally up on the day (Wednesday).

The lower vintage was attributed to a cool Californian summer and a deliberate decision to thin company vineyards to improve quality.