On a five-year average, farmers in the 18 largest corn-growing states have completed 77 percent of their corn planting by this week. This year, only 51 percent of those corn acres have seed in the ground, the report said.

Three of those states, however, are above their five-year average this week -- Colorado, Michigan and North Carolina -- while none were above it a week ago.

Soybean planting is also behind the five-year average, with 11 percent of the ground planted compared with a five-year average 29 percent for this time of the year.

The weekly crop report said 36 percent of the nation's winter wheat crop has headed out, compared with a five-year average of 53 percent for this week of the year.

The country's six major spring wheat states are ahead of their five-year average for planting with 81 percent planted, compared with an average of 78 percent by this time of the year.