probably, assuming that the cold makes them susceptible to fungal disease... although those are very hardy and disease dettering palms. So yes, to be on the safe side.

Yes, in your case and for that zone I would treat it. Did you have them covered during the worst months?

The palms received no protection except for the fact that they were completely covered by snow from Mid December to this week. They appear to be in good shape.

You did well and to perserve them as they grow bigger I would cover them next winter. A bad winter in our zones can do damage and even kill most hardy palms.

Do you have pictures?