[CANUFNET] White Blotches on Maples

[Michael Richardson]

In response to the attached post I would like to make a few comments.  I
have been overseas so I waited until I returned home to look at some
reference materials.

First the white crust looks to me like Phlyctis sp., whitewash lichen. 
Unfortunately I cannot identify whether the crust is a lichen or fungi,
from the photograph, let alone the species.  Identification of crusts
(lichen/fungi)require morphological and biochemical testing to ensure
correct ID.  There are numerous sterile crust lichens as well as species
such as Phlyctis argena that seldom show fruiting structures, and when
they do, they tend to be sucken into the bark.  Thus a lichen cannot be
told from a fungus.

Crust fungi do not become a lichen simply by discovering a photosynthetic
partner.  Classically lichens have been considered to have a mycobiont
that is in a dependant symbiotic relation and cannot survive without the
photobiont(s) except as a spore. Essentially the fungus can only occur in
a lichenized state, it is very difficult to even propogate the mycobiont
in a lab setting.

More recent work has indicated that lichens can show a range of
lichenization from a few strands of mycobiont and photobiont intertwinned
to highly complex thallus that we readily recognize.  Thrown into the mix
are lichenicolous fungi which differ from the dominant mycobiont and may
act as parasites.

If there is a take away message it is that as professionals we should be
very careful about identification done by photograph alone.

I will collect some samples over the next few days and will attempt to
identify the organism myself.  Further I will send samples to a number of
lichenologists and mycologists who have the the biochemical and molecular
means to identify a similar crust to that shown in the original photo.

Michael


Subject: [CANUFNET] White Blotches on Maples solved

With many responses to the original post, I believe this one form M.
Burleton and J. Brown at NCC in Ottawa have solved the problem.  Thanks
Mark and James! I have quoted their response with their permission below. 
Perhaps a submission to Detective Dendro one year!

“The best case scenario I have so far is the un-lichenized fungus Julella
fallaciosa or white stain fungus. This isn't a algae partnership to make
it a true lichen. It is a crust (crustose), type of structure this why you
didn't find filament edges or scaly edges, you can find in other tree
inhabiting species.

As you know lichens are composite organisms consisting of a symbiotic
association of a fungus and a green algae living together. Lichens do not
generally harm the tree or other living matter that they a growing on-they
obtain their mineral nutrients from the air.

In some cases of the filmentose types may create heavier branches and in a
storm and could be more likely to fail because the extra weight. Growth
can seem to be stunted by heavy amounts of these lichen, but it is usually
on weaker or slower growing trees. I have seen this happen on the west
coast and in Scotland.

White stain fungus, is a "nearly" lichen, and many fungi apparently, have
acquired this mode of life.

I looked to see if fungi or lichens in my many reference books, searching
though a few internet sites and it came out to same type of lichen like
fungus.

This could be the first part of the association of a lichen with the white
stain fungus growing on the maple and looking for an algae associate.

In most cases the white patches are just the white stain fungus looking to
become a lichen and although unsightly, I don't believe it harm or kill
maples. In my woodlot at home, it is present on my young and mature sugar
and black maples. I haven't  seen any detrimental effects to them in
16yrs.”

Peter Shields
Senior Consulting Arborist
ISA BCMA ON-0570B, ISA PNW CTRA #1590, OMNR BHA #252, ASCA member
(905) 274-8300
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