Italian ryegrass like other ryegrasses will leave the soil in good condition, but it is so dogged tough and competitive that I despise it.  I'm sure it was there when you topdressed the wheat, but was small.  On a sunny day you can tell it from the wheat because the blades are very shiny.  I watch fields that have a history and scout them.  If it goes to seed in the wheat, you will obviously need to control it in the corn the following year.  What you may or may not know is that it will probably also be back in the wheat the year after that.  If you could just wipe it out of one crop, it wouldn't be so bad, but one year's going to seed will have to be fought for 2-3 years following.  It's the cover crop that keeps on giving.   :(