Contract lows set in CBOT, KCBT and MGEX wheat, with CBOT March wheat dipping to $6.00, a key psychological support level, near the closing bell.
USDA reported export inspections of US wheat in the latest week at 13.396 million bushels, below trade estimates for 16 million to 22 million.
Argentina's the Rosario exchange raised its forecast of the country's wheat harvest to 9.5 million tonnes, up 400,000 from its previous report.
Cold weather is expected to persist in the central United States this week but there was no threat of significant damage to winter wheat - meteorologist.