CORN SURGE: The price of corn rose 4 percent as crops continue to shrivel in the relentless heat wave. About 30 percent of the crop is in poor to very poor condition. Analysts say there could be more damage without significant rainfall in the next two weeks.

DEMAND FEARS: Traders are worried about the prospect of demand for commodities in the slowing global economy. Spain's borrowing costs rose again. New economic data due Friday could shed more light on China's economic slowdown.

UPS, DOWNS: Prices rose for oil, silver, wheat and soybeans. Copper, platinum and palladium fell.