North American Fruit Explorers mailing list at ibiblio

[david.maxwell@dal.ca]

Update:  I dug up the poor tree, on the principle that it was gone anyway, 
and I might be able 
to identify the cause of its demise by examining the roots.  Interestingly, 
my original thought 
of cutting off the trunk just above the root suckers might have been a better 
idea.  The roots 
in fact look healthy and intact, (although I doubt that they would survive if 
I were to try to 
replant them now).  Paring away slices of the bark of the trunk, (above 
ground level, but 
below the graft union) revealed complete loss of any apparent cambium layer 
under the bark 
of the lower trunk, and a medium brown discolouration of the wood beneath.  A 
few cm 
above this point there is still a visible cambium layer, but the wood beneath 
has areas of 
brown discolouration ranging from a few mm to pinpoint, presumably 
representative of what 
ever fungal (?) disease is plugging the vascular channels and causing the 
discolouration of 
the wood.  All these findings are confined to the Ottawa-3 rootstock; the 
Gideon cultivar 
above the graft union seems completely intact, with healthy-looking bark, 
nice bright green 
cambium, and bright white wood.  But I still have no idea what the cause of 
all this is; none of 
my books of plant diseases have anything which looks like this.  And, so far 
it is confined to 
this one single tree, with the trees on either side being unaffected.

(I did also consider that the brown discolouration of the wood might 
represent a secondary 
invasion of some rot fungus into the wood which was killed by something else. 
 Turners seek 
out wood which is beginning to rot in order to get the marbled appearance of 
what is called 
"spalting", caused by the growth of rot fungi which invade the wood after the 
tree has died.)

Any ideas gratefully received.