Buttonwood answer
 

Remember I was asking about brown patches on buttonwood leaves? Well,
I asked the owner of the bonsai to send me some leaves, because the
symptoms did not sound like rust or any of the other things the guy's
friends were telling him, and he was needlessly spraying the plant with
fungicides.

I got the leaves today and looked at them: they were covered with
minute mites (that is, really *small* mites, even for mites). Not only
that, the mites had four legs pointing forward and four pointing
backward, which to me (not an entomologist) spells eriophyid mite. And
eriophyid mites cause warty rusty patches on leaves of many hosts (I
had a button*bush* (genus cephalanthus)that had red patches on it for
years caused by an eriophyid mite). So I did a Google search of
"Conocarpus eriophyid" and got the following:

"ORNAMENTALS, WOODY PLANTS AND PALMS:
Conocarpus erectus var. sericeus (silver buttonwood, a native
species)-- Aceria sp., an eriophyid mite: A moderate to severe
infestation was found at a restored wetland in Pembroke Pines (Broward
County; E2001-4181; Maria S. Quintanilla and Dr. W.C. 'Cal' Welbourn;
10 October 2001). This probably is a new species. It is likely to be
responsible for the recent leaf distortion damage observed on
buttonwood trees in South Florida. Pruning will temporarily eliminate
the damage because most of the mites are in the growing tips; however,
in time, populations rebuild and damage re-appears (Dr. W.C. 'Cal'
Welbourn)."


So that's what I'm sayin'. I'm going to have to tell him to talk to
Florida Cooperative Extension on what miticide to use.

Nina.