Maitake Mushroom Has Flies

I have a problem with the maitake mushroom we got earlier in the season. It is still in its plastic autoclave cover, but it seems to have developed a swarm of flies--small, like fruit flies. They are black. What can I use to get rid of the flies, that will not hurt the mushroom? (I don't want to get a lizard.) Also, when your literature describes the mushroom as slow growing, just how slow is slow? It doesn't even seem to have pinned all over yet, and it's been a few months now.

Pinning may only occur on the top of the block where the bag was pulled up to form a tent shape. If you have gnats on your mushroom culture medium they may have gotten in because the tie closure was too loose.
The pinning should start in about two months after you received it. Are you keeping the bag at 60 to 65 degrees Fahrenheit? Are you keeping the humidity around it at 80 to 90%? Do you have the bag in a shady but not dark place?
The maqggots of the gnats may have eaten the mushroom mycelium and in this way prevented fruiting. The culture may well be ruined. You could try squashing the gnats one by one between the folds of the plastic bag until no more hatch, but it may be in vain. You could put a sticky strip into the bag by opening it very briefly and let it catch the adult gnats. (Richters catalogue #T2260)