Same as the fig whitefly that is decimating Ficus in Broward. Media attention has been non-existent and many hedges are far too gone to save at this point. Yeah, yeah, many people hate Ficus hedges, me included, but the whitefly affects the whole genus which is far more than F. benjamina.

I'm not sure what mites look like when they've been at palms, as I said I havn't the foggiest about them, the link martin kindly provided makes me think it might be leaf spot, I have the pictures now. The blotches seem almost like a snake skin.

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

Haven't seen one looking like that before. Appears to be a well established tree. I'd say it's getting too much water. They like to be kept moist but not soggy.