Above is the main ingredient that many are recommending be sprayed on boxwood. This is a photo taken at a Lowes Home Improvement Store. For $14, you can get enough to mix up 64 gallons of chemical. It does need to be sprayed on 7-14 day intervals because it's only a contact. I personally mix this with a systemic fungicide that gets in the plant.
Think of this like a human and someone with a rash. It neccesary to have ointment to put in topical to control the symptoms and even stop it from spreading. However, taking a pill, possibly an antibiotic, will fight the infection from the inside. This is the very reason I am confused by those people recommending only contact fungicides. In the world of Turfgrass science, we always mix chemistries to combat diseases with different modes of action.
Above, I really got a kick out of this. This product is Bifenthrin, which is very effective killing the adult stage of most insects, including Yellowjackets. Based upon the note that was left at the store, this individual didn't feel it worked. There is no telling what he was trying to do with it because if used correctly, there is no reason it wouldn't work.