I cannot even imagine Tillandsia being so prevalent that they would weaken a mature tree. In the deep southern states in the US, our oaks (particularly the "Live Oak") and cypress trees are absolutely loaded with Spanish moss, a Tillandsia. As dense as this species gets, I have never heard of them harming a mature tree. As far as I know there are no Tillandsia that are parasitic. It is interesting that they would be considered a danger in cities in Argentina.
