The problem with most mycorrhizae is concentration-in a product like Orca, they take an already small amount of mycorrhizae, dilute is even more with water, then have you add that to an even more massive amount of water before you feed your plants...of course it doesn't do anything. For mycorrhizae to work, you need a high concentration of it directly touching your roots. Compare the concentration found in various products, it varies wildly even in supposedly good, powdered products. The only one I use anymore is Dynomyco-at 900 propagules per gram, it's by far the most potent on the market, AND it's made in Israel, which sounds good to me for some reason lol. Enough studies back it's use in agriculture, I think most people just don't use the right product.