Mmm..is that a mix of pics there ... me-thinks not all of the same specimen...are some googled images????.
What is the precise location of this Phoenix palm ... that may well be salt-burn if its close to the ocean.
Fusarium wilt of palms - Botanic Gardens Trust - Sydney, Australia
I dont see the tell-tale discoloration of the vascular tissue in the shafts as you would expect with Fusarium wilt.
It is a systemic disease, spreading from the ground up thru' the vascular system...the presence of mould dust on the trunk is probably just an unrelated opportunist IMO. (I could VERY well be wrong there).
Seems like the diagnostic confirmation is no so straight forward either.
A bit more case history would be good...especially IF it is a transplant (?)