Honey Mushrooms are Tree killers?

Tom Volk tjvolk at facstaff.wisc.edu
Wed Feb 8 11:10:24 EST 1995

Hi John. This is with regard to your Armillaria problem.

In article <3grrvk$ltt at onramp.arc.nasa.gov> watson at pioneer.arc.nasa.gov (John S. Watson - FSC) writes:

>Recently the brich in front of my parents house all died,
>and around them were a bunch of small muchrooms that looked like
>honey mushrooms, ( Armillariella [= Armillaria] mella ).
>At a friends house near here I recently found much bigger
>honey mushrooms all around 3 of his tree. 
>Acording to David Aura's book "Mushroom's Demystified",
>honey mushrooms are parasite for which there is no cure,
>and which eventually kills the host tree.
>So does anyone know anymore about these guys?  Is there
>anything that can be done except sit back and enjoy the mushrooms?
>So, are all these trees doomed?  How long does it take to kill them?
>Should trees killed by them be replaced in the same area, 
>and and should we wait a while to do so?

As you probably know, what we used to call Armillaria mellea has been split 
up into 9-10 species of Armillaria in this country (aboutt 35-40 species 
worldwide).  These are defined by matings as biological species.  This is 
certaily not a purely academic exercise fromt he standpoint of patholoy.  
The different species vary widely in their pathogenicity and many are specif 
to hardwood or conifer.  For example true Armilllaria mellea (Vahl:Fr) 
Kummer can be e sever pathogen of hardwoods, and doesn't occur much on 
conifer.  Armillaria gallica Marxm. & Romagn (= A.bulbosa Velen.) is 
probably the most common species in the east, and is not very pathogenic.  
Evidence indicate it is probably just saprophytic.  Armillaria ostoyae 
(Romagn.) Herink is normally a severe pathogen of conifers, but also occurs 
nearly half the time on hardwoods.
I can't tell for sure from your post, but I think you;re in California.  One 
study in California has addressed this problem.
Jacobs, K.A. et al  Identification of Armillaria species in California.  
Mycologia 86:113-116, 1994
Much more work needs to be done on pathogenicity of the various species in 
different parts of the country.
What is clear, however, is that your birch tree is doomed.  Once Armillaria 
takes hold, the rhizomorps and mycelial fans penetrate under the bark of the 
roots and the "butt " of the tree and destroy the cambial layer, everntually 
girdling the tree.
As MycoChef pointed out, though, they are delicious.  I have noted no real 
difference in flavor in any of the species, although you certainly want to 
cook them *very* well in any case.  there are several reports of illness 
from eating undercooked Armillarias.
This may be much more than you wanted to know, but it's kind of interesting 
to me-- I am in volved in writing a monograph of the North temperate species 
of Armillaria at present.  Fell free to write if you have queestions.
Tom Volk, Center for Forest Mycology research, Forest Products Lab, Forest 
Service, Madison Wisconsin   tjvolk at facstaff.wisc.edu

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