* CBOT December corn, which represents the crop that will be harvested this autumn, dropped 2 cents, or 0.6%, to $3.66-1/4 per bushel. The contract traded near a three-month low reached on Friday.

* Soybean futures fell 1%, adding pressure on the corn market.

* The US Department of Agriculture late on Monday increased its good-to-excellent ratings for corn and soybeans.

* The USDA said 27% of the corn crop had reached the dent stage of development, well behind the five-year average of 46%.

* Traders and farmers are uncertain about the size of their upcoming harvests after heavy rains and floods disrupted plantings this spring.