No problems at this time with my flock. Of course being new to raising "chicken nuggets" as my grandson calls them I have read some of the problems people are having and kind of relating these problems and solutions to what I have learned raising different animals in the past. I'm actually not freaking out about stuff, just yet.
If you aren't having any trouble, preventative measures will do most of the work for you.
So far I have been nearly three years of mite/louse/fly/roach free chicken keeping. I keep a poop board under the roost and fill it with Sweet PDZ which is a horse stall freshener. It clumps like cat litter and I scoop it once a day as part of my morning routine. This massively reduces the amount of droppings in the coop, and things stay nice and dry (and smelling pretty good) so flies aren't attracted. I've seen a fly or two get caught in the coop before but I have never had FLIES! like some do.
I also mix a small amount of Ditomaceous Earth (food grade only!) into the bedding and nesting areas. Some people debate if it is as good at killing bugs as others think-- honestly, even if it was proven not to kill insects, I'd still use it because it is a great desiccant. It dries up any mess or poo quickly.
I also feed a really high quality feed with not much filler, and my girls seem to poo less and it's rarely loose or very smelly. This is a personal choice though because out of all of my chicken keeping habits, it is the most expensive one.
I also meal feed my birds and keep all feed inside. Essentially, I don't let them spill it all over, which can attract roaches and mice/rats/etc.. and it is never in a situation where the feed can get wet.. that's a whole other set of problems! Roaches aren't a big problem here but they were when I lived down south so I always try to do things to prevent them anyhow.
I provide the girls with a dust bathing area, and mix sand, some Diatmoaceous Earth, and wood ash into it. I am not one of those that thinks that DE is a cure all by any means, but I think it can help as part of an overall regimen to reduce the incidence of some invertebrates. In this way the girls dust themselves with some preventative. If I ever discover mites or lice on my birds I would absolutely use something stronger to dust them with but until then I try to introduce as few toxins as possible.
I keep wasps, hornet, and bees from setting up shop in my coop by covering my (hardware cloth) vents with some simple window screening.
I occasionally get a few spiders. If the girls can catch them, they will eat them! If not, I usually let them stay to clean up any other insects that get into the coop. This has taken me some time as I am afraid of spiders, but rationally I know that most species can't harm me.
Other bugs... well, there is no realistic way to control them where I am. I am looking at mosquitoes and we also get a black fly hatch here in the northeast, in the spring.
