It's not a disease. It's probably black spot which is a fungus. It happened to my potted trachy (entire fronds had black spots on it) and it happens on my tropical palms from time to time as well. It goes away on it's own. Usually the cause of it is the fronds staying wet for a long time, if you got hit by the heavy rain lately like I did by me, that could be a reason why it happened. Just don't get the fronds wet when watering and make sure sprinklers arent hitting it. A fungicide might help also, but the problem shouldn't be life threatening for the palm at all.
Good luck!
-Alex

Alex. Thank you so much for your advice. Your right on, we did have rain for a couple of days in a row. I will treat with a fungicide like you said.

Thank you again,
Joe