I had a conversation with Scott Woodbury from the Shaw Nature Reserve about their use of Mycorrhizae in the production of their plants.
They initially use a potting mix which is 50% mix from St. Louis Composting plus 50% BX-ProMix. BX already has some Mycorrhizae in their mix.
When they transplant the seedlings to their own pots, they add Mycorrhizae. The brand they use is http://mycobloom.com/
He has had good results with this brand. Scott wrote am interesting article about Mycorrhizae in the Kansas City Gardener.
While the initial price of this product – $20 for two pounds, seems a bit high, when you consider that many plants cost $10 or more, then if you could save just a few plants using Mycorrhizae, then the price would be justified.
Scott did mention that they had not done field tests, but that they great results in the greenhouse.
According to the Myco bag, you are supposed to add 2.5% by volume.
Doing the math, my potting soil container is 9″ x 14″ x 5″ = 630 cu. inches
630 x .025 = 15.75 cu. inches = 1.1 cup of Myco for my full container.
Below is a good video on mycorrhizal fungi.
Butterfly Gardening 