http://www.bonsaioutlet.com/myconox-bonsai-tree-mycorrhizal-inoculant/
Search "myconox" lots of info
Somehow my original post got garbled...
I have checked my roots/rootball, and have not seen any sign of the white mycorrhizal growing. Is it usually found on wild trees? Would you expect it to be found on the roots of nursery stock?
It is usually found on wild trees, pretty much without exception. It can be hard to see or the mycelium you do see may be a nonsymbiont, wood decay fungi. But through tissue sampling on petri dishes its been found that fungi are always present in all land plants, from the roots to the tip of the foliage. All interacting in complex ways, communication pathways, nutrient transferring, pathogen suppressing, increasing drought and thermal tolerances, quite fascinating.
Its likely present to a degree in nursery stock, fairly common nowadays for nurseries to include innoculants somewhere along the line transplanting or germinating. As well its present in the environment and will find its way to a good home eventually.
I prefer to not introduce species from elsewhere such as those products but I have trees healthy and packed with the stuff and do some cross watering into trees of the same species sometimes, recipients being weak or transplants.
General rule of thumb, pathogens thrive in anaerobic conditions, and benificial organisms like aerobic. No coincidence as roots lacking oxygen are weak and more prone to infection. Provide friendly conditions and they will come.
If I lived elsewhere, city or something I would probably use a product like that.