Hmm, I'm not sure what those are, though they do kind of look like scale. The scale insects I find on my plants (I live in Minnesota) usually have a brown, hard little body. Things I have used in the past to treat my Rabbit's foot fern for scale include: (1) watered-down alcohol; (2) soapy water.

I used a little sprayer/mister to apply it, and I think I repeated after a few days. None of this stuff should hurt the fern. Because I have done this in a sort of inexact, unscientific way, I can't say what did the trick, but I haven't had problems since.

Good luck!

Those are young wax scales, and are difficult to control. One of the most effective methods would be to apply horticultural oils, which you should not do to ferns.