I believe the best way to use pesticides effectively and safely is to always use an effective material against the targeted pest, spray at the right point in the insects life cycle at the proper rate and only spray when necessary. Integrated Pest Management is the buzz word that describes this approach.
Some insecticides are broad spectrum and kill most of the the bad bugs and most of the good bugs as well. Some insecticides only kill certain insects and are easy on beneficials, so its important to know what problems you are trying to solve. Spraying the wrong stuff or at the wrong time is a waste of time and money and can create other problems. This targeted approach requires more knowledge and patience.
The Signal Word on the label as well as the PHI and REI are some good indications of the safety of the pesticide. However, the PHI for any given material may vary a lot from fruit to fruit and I’m not sure why. The label also defines the correct type of protective equipment to be used. I always wear a respirator even if the label does not require one.