How well is your shed sealed? If you have open gaps and your not putting some kind of filter on your intake then you are going to have insane bug problems. I would seriously suggest trying to get a good population of predatory insects, start with ladybugs, if they get out of control just get a couple preying mantis.
The best thing to do is to not get bugs in the first place, but I dont think thats an option for you so its going to be a constant battle, your not gonna want to use chems all the time, so I would seriously suggest setting up some defense, get on the bugs before you actually start to notice them, once you realize mites are there its too late to prevent them and its time to start the fight.
Also set up a perimeter, get some raid drops and stuff and go around the shed (on the outside)