Dear Beeman, I have used FGMO since the spring of 1997. I had apistan on very early that year and when tested found no varroa. Mostly checked drone brood and did ether roll in each apiary. The bee inspecter and I did more testing this past week. We found varroa in 3 out of 4 apiaries ( have 14 hives). One hive was full of mites. Although they produced 3 shallows of honey which is rare for this area of Maryland. They also were very strong and were preparing to swarm. Split the hive. BUT we did NOT see varroa in the brood!!?? The ether roll showed about 25 to 35% infestation. Have used the FGMO about every 2 to 3 weeks since early Spring. I put it on every frame (top bars) in the hive leaving a small line of the oil on each frame. ( Use honey bear with small hole). After losing about half of my bees for the past several years using the other methods, I was pleased to have only lost one hive this past winter. It makes me wonder how much the varroa affects the bees and how much maybe the T- mites do. Or was it just the mild winter we had. Or are the only mites left, those that don't kill the host. Or does the FGMO keep the population down? I can't assertain what it does to the T - mites. Don't have the microscope. I plan to watch the hive with the mites closely. I did another ether roll yesterday and found the same 25 to 35 % infestation. And again no mites in the brood!!?? Billy Bee