CV,
Several years back, I was actually looking around for a source for dallisgrass seed to add to the sward here for more warm-season grazing. Was noticing a couple of nice patches of it on the side of the highway on the way home, and even considered stopping and hand-harvesting some seed.
Then... all of a sudden, BAM! it appeared in the pastures. It was Everywhere. Don't know how long it'll stay before taking a hiatus, but it's come back every summer since. No major problems with ergot, so far.