My mini experiment with OMF over two winters and three summers in Maine
has proven to me that they are not all they are cracked up to be, at
least in cooler climates. Granted, mine is only one data point, but the
results seem to correlate with the weather we experience in Maine.

I have two hives on omf and one control with a solid bottom, so the
experiment is not all that rigorous, but the results track with what I
would expect with lots of ventilation. In Maine, we can go from hot to
cold in a day in the middle of summer. We had a cool spring and did not
warm up until late. And we have had a roller coaster summer as far as
hot and cold. The day before yesterday we had fans running and I was
wearing shorts. Yesterday I was wearing a sweatshirt and long pants and
today is only a bit warmer.

The cool summer is reflected in the strength of my colonies. The closed
bottom hive is out performing both omf hives in number of bees and
nectar brought in. To me, the omf hives are having to expend more energy
keeping the hives warm than the closed bottoms and that, over the
season, has put them at a disadvantage. The difference is very
noticeable.

How they handled varroa is still to come. But right now, my method of
use for omf will be to keep them closed except when I treat for varroa
or run drop tests. No more leaving them open all season.

Bill Truesdell
Bath, Maine