At the farm we're finding there is a balance in nature.
We've had pretty good luck with "normal" infestations in the long run with mostly organic controls and habitat management. A lot of the wasps are your little friends, we have a massive collection of the little predatory wasps out front on some of the catnip and other flowering plants. They also eat a ton of aphids and other undesirables. Planting predatory bug attractants (dill, fennel, and related, apparerntly catnip helps also, plus marigold & zinia deter a lot of bugs and provides food for good ones). If you try to eradicate to much you're left with an infestation of whatever those were feeding on.
The one kind of wasp I won't really tolerate to much are the meat bees, I usually trap those if they start hanging around the patio to much.. I've had good luck with leaving some BBQ chicken bones out whereever they are and then moving the bones slowly closer to the trap over an afternoon (don't put them in the trap right away), around 9-10 at night THEN put the bones in the trap. The next morning they'll come out to resume the feast and by then the whole nest knows about it so they show up en-force and all enter the trap as a unit. I've pretty much filled those yellow wasp traps in one day with this trick. Most of the other wasps though are garden friends so I leave them alone unless they're actively on a building. Oh and I guess the one species of super aggressive evil ground dwelling bees we have here.. those get sprayed because they're just evil (I usually don't get sick from stings but 6 of those and I was out for the afternoon).
Generally flies means there's fly habitat, so I guess figure out what that is and how to manage it. I had a bit of a fly situation on the compost a month or so ago when I slacked at managing it but once I turned and topped it properly that went entirely away.
For the stagnant ponds a teaspoon or so of veg oil applied weekly (or more often if the water moves much) works about as well as a lot of the mosquito dunks.
Earwigs though, we've gone fully medieval on those and have been putting out in-ground water traps (tupperware filled 1/2 with water, soy sauce, veg oil), spinosads spray, sluggo plus spinosad bait, diatomaceous earth dusting.. hand picking, cardboard traps (wet, leave overnight, burn in the morning).
We also had a terrible infestation of the invasive California Grey Digger ground squirrels (which are non native here and wreak havoc on the native habitat). I had quite a trapping adventure removing those back to at least the perimeter of the main parts of the property. I made a bunch of trap boxes to keep out dogs, skunks, children, deer? and use conibear 110 traps inside of those which worked really well. I'm kind of half live & let live but eat my cabbage and bean crop and the war is on.
