> Do others find that there are more mite problems in larger apiaries ? 

Certainly, Randy. But that doesn't mean that small apiaries can't have problems.
You need at least 8-10 kg of good quality pollen pro colony from july till november (my area) to get fat and healthy winterbees who can handle deseases and mites.
Is it then so astonishing that larger apiaries have difficulties to reach this and get more mite problems ?
All depends on the availibility of good food (especially pollen for winterbees) in the area and how many colonies have to live on it (your own colonies and those of all your neighbour beekeepers in the same area).
When I see some pictures of big beeks who collect all their colonies (hundreds) on overwintering yards, they look like graveyards to me
Marc

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