I was told that they can be toxic if kept in close quarters with a snake/reptile. Also, I've heard that they can contaminate water that is left in a water dish if it's around a pest strip.
If your going to use a pest strip, I would start with small pieces and not have them too close to the reptiles. Try putting a small piece in a jar with holes in the lid. This way no one can come into contact with the pest strip and it still kills the bugs.
Maybe it will be enough to kill the flies without overdoing it and exposing too much of that stuff to the reptiles.
If there is anything the nonconformist hates worse than a conformist, it's another nonconformist who doesn't conform to the prevailing standard of nonconformity.