I recently started brewing my own earthworm castings tea and have found this info, dunno how valid it is but it states......Liquid worm casting is a rather powerful and effective kind of an insect repellant that can kill white flies, aphids and spider mites. These are harmful insects that suck out the juice from your lovely indoor plants. Yet, it is gentle on your plant. You can even prevent and help your indoor house plant fight fungal infections and common diseases like black spot, rust, powdery mildew and several other types of common pathogens.
If this is true no matter what the the original poster has (mites or rust fungus) foliar earthworm tea will def help. I haven't tried it foliar yet but I just added my first batch to my res this morning. With any luck it will help with whatever it is I and the original poster had/have.
I've also read that a solution of garlic and water works as a cure for rust fungus.