Found these definitions on a website dedicated to fungus:

http://www.plant.uga.edu/mycology-herbarium/whatis.htm

Macrofungus (macromycete) - The term macrofungus is used for large fungi
that are readily visible to the unaided eye, such as the mushrooms,
puffballs, and many cup fungi. Even so, detailed study of macrofungi must be
conducted with the aid of a microscope, due to the small size of the
reproductive structures.

Microfungus (micromycete) - The term microfungus, meaning small fungus, is
used for fungi in which a microscope must be used for even casual
observation of the spore-producing structures. The majority of fungi are
microfungi and their study requires experience with the use of microscopes.

If this is the only meaning to the term and if it does not refer to a
specific fungus or group of fungus than "microfungus" means nothing
different from the term "fungus" as I generally see it used in this
newsgroup and applied to fungual infections of our plants. Of coarse there
are probably lots of fungus pathogens that do other nasty things to our
plants besides cause rot.

"Al" wrote in message news:...
How is a microfungus different from the regular fungus that we as orchid
growers are always battling? (You know, the stuff we call 'rots' and
which
could as likely be a bacterial infection.)