You're right on total wheat acres planted:

• Corn Planted Acreage Up 19 Percent from 2006
• Soybean Acreage Down 15 Percent
• All Wheat Acreage Up 6 Percent

(According to this site: http://www.ethanolmarket.com/corngrains.html)

For other people who want to look into this, the NASS database query page is here: http://www.nass.usda.gov/QuickStats/Create_Federal_All.jsp)

Wheat and corn don't really grow in the same places, whereas soybeans and corn to, so I think the greater point is valid. Where farmers can shift to corn, they have, meaning less of whatever the alternative crop would have been--and that choice affects the choices other farms make with regard to whatever alternatives they have. Since (unlike corn) many of those other grains are partial substitues for wheat, less of them still puts price pressure on wheat.

There's a lot of press out there about acres shifted to corn, which I suppose refer to a lot of specific situations and changes versus what was possible. I link to one in the post, and the topic is addressed in the link above.

There are also a lot of particular situations. For example, there was a drop in spring wheat, which is the one that would be most affected by rising corn prices, as that's the acreage where the decision could be made later.