December corn opened 4 1/4 cents lower on the session at 720 and experienced an early range 704 1/2 to 721. Less concerns for frost or freeze damage helped spark the lower opening and fund traders were active sellers to help drive the market to the lowest level since August 11th. Even strong export sales, higher energy and weakness in the dollar failed to provide much support. Weekly export sales for corn came in at 1.127 million tonnes for old crop and 41,100 for the next marketing year which was about twice the sales expected. As of September 8th, cumulative corn sales stand at 34.4% of the USDA forecast for 2011/2012 (current) marketing year versus a 5 year average of 25.2%. Sales of 536,000 metric tonnes are needed each week to reach the USDA forecast. Temperatures lows in northern Iowa were near freezing which had traders believing that damage might be limited except for corn which was not mature in the northern half of Minnesota. Speculative long liquidation selling seems to be the primary bearish force today and a sharp break in precious metals may have added to the negative tone.