A question first, are you already doing insect/disease applications? If not, I would say don't do it. My experience in this area says that most markets already have more applicators than are really necessary. So then people are "forced" to sell more pesticide applications to make owning the equipment worth it. This sets up a scenario where a given area is overly saturated with pesticides and no one really tracking how much chemical we are actually putting into the environment.
I believe that part of being a "good tree guy" is also being a good steward of the environment. Look at these 2 articles.