Major American food stores have begun rationing sales of rice to prevent stockpiling by customers who are worried by the soaring price of staple foods.
The global price of rice has risen 68 per cent since the start of 2008 and, in some American shops, has recently doubled.
There was little evidence of panic-buying by individuals but restaurants and small shopkeepers were stacking up on supplies in case costs rose further.
In response to what it called "recent supply and demand trends", Wal-Mart's cash-and-carry division Sam's Club is limiting customers to four 9kg bags each to prevent a run on stock.
Managers at some branches of Costco, the US's biggest cash-and-carry supplier, are limiting sales of rice and flour. The firm's chief executive James Sinegal said he believed media reports of global food shortages had fuelled the surge.
Tim Johnson, president of California Rice Commission, which represents the state's growers and millers, said: "This is unprecedented. Americans, particularly in states such as California, have on occasion walked into a supermarket after a natural disaster and seen the shelves less full than usual but we have never experienced this."
But he added: "Bottom line, there is no rice shortage in the United States. We have supplies."
The price of staple foods has rocketed worldwide in the past two years because of rising demand from developing countries including China and India, high oil prices and increased demand for biofuels – corn is used to make the fuel ethanol – which has also had a knock-on effect on the price of livestock feed.
World rice stocks are at their lowest since the Bangladesh famine of the mid-70s and production this year is not expected to meet the 430 million tonnes likely to be consumed globally.
The situation has boiled over into mass protests, riots and looting in countries including Mauritania, Senegal, Yemen, Guinea, Mexico, Morocco and Uzbekistan. In Haiti, the price of rice, beans and fruit rose by 50 per cent in the past year. Six people died in demonstrations earlier this month. Since January, big rice-producing nations including India, China, Vietnam and Egypt have capped exports.Reuse content