I purchased 4 bales and used the ratchet straps
on them and built an enclosure with a plastic corrugated roof . This set up for target works great my question is should you take the plastic wrap off the bales or leave it on to keep dampness out your thoughts ! thanks
   ---------Black Wolf 68"57#@28"--------
   ---------Tall Tines 60"52#@28"--------
   ---------Tall Tines 60"45#@28"--------

Take it off, I think.  As soon as it gets a few arrow holes in it, it becomes a trap for any moisture that gets blown into it, which will decay and mildew the bales.  Since you have a cover over the bales, a little moisture shouldn't hurt - as long as it can get air circulation to dry out.

I have to agree with Rough Run. We found the moisture (rain) the soaked in from the top of the bales ruined them faster. Covering them as you have done will prevent this. I assume this setup is in your yard? If I had that setup and was still concerned I would rig up some kind of drop cloth to protect the bale that could be used as neede in a rainstorm. Then rolled up agian after rain stopped.

Remove the plastic and keep them covered from above.

What they said - take the plastic wrap off. Or they will rot.