[NAFEX] Dying tree

Christopher Kennel ckennel at gmail.com
Sun Jul 24 15:23:46 EDT 2011


David,

I'm no expert on tree diseases, and I don't know where the tree in question
is located, but I do make regular use of Insects and Diseases of Woody
Plants of the Central Rockies as a volunteer master gardener.  It has a nice
diagnostic key, and from your description of the damage and rapid onset and
if this tree were in Colorado, I'd nominate verticillium wilt as the most
likely cause.  The pathogen a soil-borne fungus, but infection can occur
above ground in places where the bark has been damaged.  My second choice
would be a stem decay fungus, but there are many types of these.  Wind-blown
stem decay fungi spores infect trees through bark wounds.  The bright orange
bark sounds interesting, and I'd like to see a photo of it.  If it is
related to the infection, it could be caused by fungal fruiting bodies.

All the best,
Chris Kennel
Denver, CO z5

On Sun, Jul 24, 2011 at 11:43 AM, <david.maxwell at dal.ca> wrote:

I am most grateful to all those who have offerred advice and comments.  But
> I don't think we
> have this nailed down yet.  Michelle, I do not think it is "Brown Line
> Decline"  I sectioned the
> trunk starting at ground level.  At this point the wood is clean and white.
>  The bark is quite a
> bright orange, and i am a little uncertain whether this represents disease.
>  Starting about 8
> cm above ground level there is a little discoluration of the wood and an
> area of blackening of
> the bark.  As one proceeds up the trunk the discolouration in the wood
> becomes more and
> more prominent and obvious, giving a mottled appearance.  The bark at these
> levels has a
> clear area of necrosis, with a blackened appearance under the bark, which
> is separating. The
> maximum staining of the wood occurs between 24 and 30 cm., and above this,
> the bark is
> slightly darker in a small area, and only the heartwood is discoloured. The
> graft union is at
> about 40 cm and here there is only a minimal staining of the heartwood, but
> persistence of
> the small area of darker bark.  Above the graft union the Gideon cultivar
> looks absolutely
> clean, with green cambium and intact bark.
> My analysis is that whatever this is penetrated the bark at about 24 cm
> above ground level,
> and spread a little down, and up as far as the graft union, but not beyond
> it.  Judging by the
> staining of the wood, it has been present for a number of years.  (The tree
> was grafted in
> 2001).  The interesting thing is the absence of external evidence of
> cankers or anything to
> suggest what was going on under the bark.
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