I have dense ferns on the north side of my house and they are being eaten...
I have dense ferns on the north side of my house and they are being eaten away, leaving the skeleton of the frond. I don't see any insect, slug or caterpillar. Any ideas and how do I kill or treat whatever it is. I noticed it last year but was not quite as bad. Thank you for any help. Norma
Hennepin County Minnesota ferns
There are several diseases that may cause the kind of damage you are describing.
Here is a link that discusses them. Perhaps you will be able to identify what is going on with your ferns:
As far as insects go, fern scale is probably the only thing that affects ferns: