next message in archive
next message in thread
previous message in archive
previous message in thread
Index of Subjects
Index of Subjects
Peter Payzant wrote:
> Thanks to David, Chris, Paul and Jim for enlightening me on this
> subject. I take it, then, that although the outer surface of the bark
> has a steady arrival of fungal spores, they don't develop there,
> mostly due to the dry environment. The failure to develop is not due
> to any defences that the tree may be producing.
>
> If they can get inside the bark, by whatever means, they then grow.
> Some species will grow outward through the bark where they appear as
> "bracket" fungi.
>
> Is this more or less correct?
>
> Peter
>
Hi Peter & All, Dec 20, 2006
That is a fair statement of the typical, I think. I wouldn't be too
sure that chemical defences are always absent.
There are always exceptions. Trembling Aspen (and _Populus_ in
general) may be one of the exceptions in that various Cankers seem able
to invade intact bark. But Populus outer bark (and epidermis ?) also
remains live for about 10 years and entry may be via stomata or initial
fissures in the epidermis. Collar rot, of e.g. Apple, does not need a
wound I think but is favoured by conditions that keep the bark just
above soil level moist. Details escape me now but I do recall once
seeing fog condensing on _Populus_ bark, past the point of runoff, and
wondering if this helped Canker invade. Other nearby tree species were
dry I think.
As we know from numerous examples, some fungi invade leaf tissue so
it is at least possible that some manage to invade wood via this route.
Perhaps some Plant Pathologist could comment on this entire subject.
A bracket fungus that is quite common on _Populus_ (dark, stubby,
pore fungus; _Fomes_?) is my cue that the tree is too far gone to cut
for firewood, even if there is still substantial live top. By the time
those brackets have developed, most of the heartwood will have lost ~1/2
or more of the original dry weight.
Yours truly, Dave Webster, Kentville
next message in archive
next message in thread
previous message in archive
previous message in thread
Index of Subjects