Way back, when I was brand new beekeeper in the early 90s, I sent a letter to the editor of Gleanings that said we were breeding for Varroa because of cell size. It got little response. When I finally got on the internet, I searched for research that proved my supposition. There was on study done and it disproved it, but not conclusively. If my memory is correct, it was done in Sweden by a grad student. So there is at least one study and it is in accord with Mike Allsopp's comments on cell size and its lack of effect on varroa. I did try smaller size foundation on my hives about six years ago and had excellent success until last winter. But two years ago I added different plastic foundation to my three hives to trial the differences between them. As editor of our state newsletter, my experiments are a good source of articles, especially on what not to do :) So, did the larger plastic foundation cell size cause my hive loss or was it apistan resistant varroa or were my naturally mated queens now more susceptible to varroa or was it really tracheal or was it bad honey or was it robbing from a new beekeeper's hives in the area or was it.... Any of those things could have caused the loss of two of my colonies. But, if I were an earnest proponent of small cell size, then obviously the introduction of larger plastic foundation cell size is the reason. I would disregard all else. There are too many variables out there to say it works. We have different Varroa. Many of us allow natural requeening so we select for our area as well as mite tolerance. So we have different bees as well as different varroa. We may be in an area that Varroa is absent because all the feral colonies were killed off. The bees may forage on nectar or pollen that naturally controls varroa. Our own beekeeping practices, like smoking the hives or not, and with what kind of fuel can influence varroa numbers. Do we use screened bottom boards. Pollen traps. I think you get the picture. With the number of variables out there, without controlled tests, we are no better than my letter to the editor, a reasoned guess. The guess may be correct, but I originally thought FGMO was too. And in view of Mike Allsopp's comments, we may be looking at the wrong reason that some are enjoying success with small cell size. Bill Truesdell Bath, ME