US snack maker Diamond Foods has upped its forecast for annual earnings after a first quarter of bumper snack sales - although the company predicted a weaker second quarter.

The company lifted its target for full-year earnings per share from US$1.70-1.80 to $1.72-1.82 after first-quarter snack sales climbed 64% to $60m.

Diamond said its snack sales were boosted by a full quarter's contribution from Pop Secret, which the group acquired from General Mills in 2008.

President and CEO Michael Mendes also praised Diamond's Emerald brand. "Emerald set a new quarterly sales record as it achieved significant sales gains from successful new products, filling distribution voids and more effective merchandising," Mendes said.

"Based upon this strong performance and the expanded marketing initiatives planned during the next several months, we are raising full-year fiscal 2010 EPS guidance."

First-quarter earnings per share stood at $0.88; adjusted EBITDA rose 27% to $29m.

However, despite the leap in snack sales, Diamond's turnover fell 8% to $180.6m due to a later walnut crop harvest, streamlining of the company's product portfolio and softer commodity prices meaning "greater value being passed on to customers", the company said.

Looking ahead to Diamond's fiscal second quarter, the company said it expects sales and earnings per share to be lower than its first quarter.

It forecast sales of $170-175m and earnings per share of $0.42-0.46.