On 3 Jun 2006, at 22:26, uktc-request@xxxxxx.tree-care.info wrote:
Date: Sat, 3 Jun 2006 13:33:31 +0100
From: "Mike Ellison" <mike@xxxxx.co.uk>
Subject: RE: Dead, Dying, Dangerous Query
Hi Scott
SC - I did see some research from Western US that stumps can provide a
massive food source for aggressive Armillaria sp. (I'd guess mellea
but not
sure) and that infection areas obviously spread from cleared areas
(e.g.
blowdown patches) where stumps had been left.
ME - Well that is my point. When we know that the fungus decays
non-functional xylem, it doesn't take much or any research to
conclude that
the fungus will decay dead stumps.
SC - No doubt there are many other variables involved and I'm sure
you have
to be familiar with local host/pathogen/climate/soils relationships
to know
when it matters.
ME - It seems to matter particularly where there are environmental
stresses
resulting from disturbance (clear felling and extraction) and reduced
biodiversity. I guess that escalating organised crime in Eastern
Europe
following disturbance of a social equilibrium is a reasonable analogy.
Mike
Mike
Hi
I agree with you in principle, but Hetero b. may be one of the
exceptions to the rule.
Your analogy perhaps applies more readily to r-strategy pests which
continually colonise habitat of an ephemeral nature or exploit rapid
changes in their environments; e.g. bacterial cankers of poplars in
forest monocultures and cereal rusts in prairie agriculture.
However, Hetero b. is a K-strategist which likes more stable
conditions and narrow niches - a specialist. As such, it is more
vulnerable to cultural controls. Just as debarking felled trees can
eliminate the potential breeding grounds for bark beetles, so removal
of Hetero b.-infected stumps can substantially reduce the risk of
infection to the next crop.
See Conway, G (1981). Man versus pests. In Theoretical Ecology (2nd
ed) (ed. R. M. May,), pp. 356-86. Blackwell Scientific Publications,
Oxford.
I grant you, my references may be out of date.
The other key issue we were taught in forestry, was correct species/
provenance choice. Most of the really dreadful problems were caused
by wrong choices, rather than necessarily, monocultures; e.g. wrong
provenance of lodgepole pine on unflushed peat in Scotland resulted
in devastating outbreaks of pine beauty moth in th elate seventies/
early eighties.
Anyway, time to get out in all that sunshine - I'm off for a pic nic
breakfast in a beech monoculture!
Regards
Adam
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