We have used wood pellets in our shelter for almost four years.  The only
time that we had a fly problem was when we foolishly decided to try and
compost them (poop and all, of course).  The flies loved it, especially
the biting kind.  Other than that we haven't noticed a lot of flies, and I
would notice because the shelter is a sunroom that we added to my kitchen.
 
We freshen boxes and cages almost every day and scrub pans twice a week.
That probably helps keep the flies down.  There are usually a few flies
around but I also have dogs and neighborhood kids coming in and out of
doors.  It may be that the wood pellets hold moisture longer than other
litters and so provide a better breeding ground for maggots and flies.  A
good argument for frequent cleaning and solid, in-tact, window screens?
 
Bobbi <+:-)
[Posted in FML issue 2694]