I have not noticed an appreciable degree of harm to my home made cultures when mites appear. Perhaps it is because so many flies remain. I have always thought the mites fed on the media, not the larvae.
What percentage of mites infesting fruit fly cultures are of a species that predates on larvae? How often does that really happen? How do you know which witch is which witch?
Also, I understand the concept of cultures becoming worse through subsequent seeding of new cultures with mite-infested stock, but I've not experienced this as a worsening problem. Despite infestation of mites, I don't have problems creating apparently mite-free cultures from previously infested ones.
It's not my intent to be confrontational, but I am interested to learn what is known on this subject. I do not sell fruit flies, but I do sell a few items that feed on them and am thus concerned to know more.
Despite raising them for many years, I've thankfully had few mite problems. Though I will say that I have purchased a few cultures over the years from others and they have been riddled with mites after a few weeks (while most are not).
I do think the concerns here are valid and that it's quite possible that my experiences are outside the norm. I've just not had much trouble with low-producing cultures or mites, over the ten or so years I've been raising fruit flies for my mantises, etc.
It is relieving to read that they don't harm frogs and that frogs might actually benefit from them.
I still maintain that the main issue with mites is that they are unsightly, but only because that has been my experience.