Your supplier should give you the training you need to micro inject. I had to get certified by mauget to use their bidrin product. It is an insecticide I have used for birch borers. I have recently been using tree tech products. It is easier to use in my opinion. I think that micro injections have their place. They are expensive and sometimes hard 'to sell', but it all depends on the customer and the situation at hand. I like using them on big elm trees for example, that has slime flux. Or, fertilizing when the roots are covered, as the previous post states. They are also useful when drift is a concern or you want to treat 'just that one tree'. Micro injections are just another a tool in your bag. When used for the right situation, they work great.