A report by the USDA this morning showing the amount of corn held by farmers and stored in grain elevators at the beginning of this month was much higher than expected has sent grain prices tumbling to 2011 lows.

As a result, the PowerShares DB Agriculture Fund (DBA) is falling by 2.3%. In the previous session, the popular ETF focused on commodities prices gained more than 2% as analysts expected a slight inventories bump.

The USDA reported inventories of 1.128 billion bushels of corn as of Sept. 1. Most traders were expecting corn stockpiles to come in below the 1-billion-bushel mark, according to a Dow Jones Newswires survey.