The following comments were provided by Dr. Wade Thomason, the Virginia Tech Small Grains Specilist.

A number of fields have experienced minor to severe armyworm feeding this fall resulting in almost complete defoliation in some cases. Now the question is how much damage has been done and whether or not the small grain crop should be replanted.
The growing point for the small grains is below the soil surface at this time (and will be until spring) so the crop can tolerate defoliation without damage to the growing point. When the worm feeding ceases, these plants should begin to regrow so replanting should not be necessary. The only case that would be different would be if the worms fed on the same plants again and again, which could ultimately use up the plant root reserves. Finally the tillers we produce in the fall are very important to grain yield and how many tillers we get depends a lot on how many heat units the crop is exposed to. A clipped plant that begins to regrow tomorrow stands to benefit from better fall conditions (warmer temperatures) than a replant situation which would likely take 10 days to emerge.