WASHINGTON — The U.S. Department of Agriculture in its latest weekly Crop Progress report indicated development of the corn crop slipped further behind average while the soybean crop gained.

The corn crop in the 18 major growing states was 40% in the dough stage as of Aug. 16, some 24 percentage points behind the 2004-08 average of 64%, the U.S.D.A. said. A week ago the gap was 22 points. The crop was six points behind the same time last year.

Further matured corn was 9% in the dent stage, well behind 26% as the five-year average, the U.S.D.A. data showed. Pollination was virtually completed at 96%, about even with 98% as the average.

But development of the soybean crop gained ground with 73% of the crop setting pods, 13 percentage points behind the five-year average of 85%. A week ago the gap was 17 points. As with corn, pollination was nearly completed with 93% of soybeans blooming in the 18 major states compared with 96% as the average.

Both corn and soybean crops in several key growing states got off to a late start this year because of wet spring planting conditions in some areas and a cooler-than-normal summer that has tended to slow crop development. The delay was especially severe in Illinois, the second largest corn and soybean producing state. As of Aug. 16, only 46% of Illinois’ corn crop was in the dough stage compared with 83% as the average, and 58% of the soybeans were blooming, well behind 87% as the average.

The condition of both crops was rated slightly better than a year ago and both were unchanged from a week earlier.

The corn crop in the 18 major states was rated 68% good to excellent as of Aug. 16, one point better than a year ago. The soybean crop was rated 66% good to excellent, four points better than at the same time last year, the U.S.D.A. said.

Harvest of the spring wheat crop also significantly lagged year ago and average. As of Aug. 16 the crop was 13% combined in the six major growing states, compared with 33% last year and 48% as the 2004-08 average. But condition of the crop was far better with 74% rated good to excellent compared with 72% a week earlier and 56% at the same time last year.