UK Tree Care - http://www.oak-wood.co.uk/uktc/
So often, we seem to be told that we have no pests or
diseases of note. I think that there is a danger of
becoming brainwashed and often we fail to spot what
should be the obvious reasons for the demise or
decline of a tree.
The trouble in this country is that we rarely
encounter biblical plagues of for example Gipsy moth,
or Elm Leaf Beetle (Too few elms anyway now!!- and we
don't have this beast in the UK.)
What we do have though is an incredibly large
assemblage of frequently encountered pest and disease
organisms. I think that this is why, as individuals,
we often say that tree pathology ?hurts our brains?.
When Tim Winter and Robert Strouts produced their
?Diagnosis of ill health in trees?
they had a clear idea that they were trying to provide
a tool by which practitioners would be able to focus
on particular organisms and physiological problems
associated with tree families and species. The tool
was to be used as part of a diagnostic procedure -
look at the end papers! and page 16.
Many out there will have a copy of the ISA Arborists?
Certification Guide. The Chapter on Problem Diagnosis
and Management was largely based on ?Plant Health
Care? principles in which the fundamental concepts are
those of ?Key Plant?, and ?Key Pest?.
Few pests or diseases will strike at all species of
trees. Thus, we can concentrate our minds on the
relatively few pests or diseases that will frequently
attack a particular tree species or family.
For the practitioner, then, start with the tree
species , genus or family - KEY PLANT
This perhaps is not emphasised strongly enough in the
Strouts and Winter book, or perhaps some of us haven?t
read it properly, and understood the nature of the
tool that we have been provided with. It is not an
?identi-kit? scrapbook to be flicked through to match
by picture only. The schema for diagnosis needs to be
followed; the book was not designed to be dipped into
and out of, looking for quick-fixes.
For each of us in our various regions, or even
countries, there will be a number of pests or diseases
that we regularly see on a particular KEY PLANT or KEY
TREE.
These are the KEY PESTS/DISEASES. The number of these
is far fewer than the total world-wide fauna and flora
of tree pathogens, and with only a little bit of
practice and experience we can quickly build up a
surprisingly extensive knowledge of the bugs and
beasties that occur in our neighbourhood.
Only a handful of pests or diseases are likely to
?kill? the client?s tree overnight.
Many of the ?lower-ranked? and persistently recurring
problems can, in time, or in a year or sequence of
years which proves particularly favourable for
it/them, compromise a tree?s prospects.
This makes the persistent recommendation and planting
of certain tree species a totally un-sustainable
approach to tree care.
Kanzan Decline ?
I have watched fascinated this year to see which
trees are showing signs of disease and pest challenge
after a mild winter (Yet another!!) and a favourable
spring. Bacterial diseases on Cherries and Plums were
guaranteed to put in an appearance and rank as
probably the most frequently reported / noticed
problems here in the NW. What is more, this year, any
one specimen was likely to produce the full pantheon
of symptoms associated with attack by this type of
pathogen. We saw, in early Spring, Bacterial oozes, or
gummoses, closely followed by blossom wilts and
mummification of many of fruitlets that did set.
Later, there were more severe leaf and shoot wilt
symptoms . Often, the evidence of the previous years?
attacks were to be seen. Cankers, and dead or poorly
leafed twigs and branches were often noted, presenting
a sickly, sparse canopy and many trees exhibited
mid-season gummoses.
Kanzan Decline - Is this a new disease I?ve missed? I
doubt it somehow. I can?t say that I?ve seen a single
cultivar of flowering cherry that has been totally
unaffected by bacterial problems this year.
The greater the stress the tree is under, the less it
is likely to be able to counter the challenge. Young
transplants or veteran garden specimens, they have all
suffered.
And just when you think it can?t get any worse,
somebody brings along a sample with leaf symptoms of
fungal scab (Venturia spp). Yes Plums and cherries
have their own Scab diseases too!
In conclusion then; the next time you are asked to
recommend a tree as a replacement for an ailing
cherry, or design a local authority planting scheme
for a residential area, use a ?new? approach.
Think about a sustainable strategy for tree health
care.
Remember your Plant or Tree Health Care principles of
Key Tree and Key Pest/Disease for your area. Look
around the neighbourhood - just don't suggest a
flowering cherry!!!
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