Need help identifying this disease/pest
I have a mature Phoenix Robellini (Pigmy Date Palm) in the front of my house where it gets full sun. I had a cluster of 2 and the one died a few years ago with a white powder. This one that stayed alive has had a very strange brown crusty substance on the underside of the leaves that makes it hard for new fronds to open up properly. This substance covers all the leaves. It gets proper fertalizer so I doubt its a deficiency. My landscaper cannot figure out what it is either. There ants that crawl all over the plant, but not sure if that is related to the problem or not. I would appreciate any help from someone who thinks they know what this is.