One downside may be that it isn't exactly legal to use, at least in the US.
Now to be self incriminating, I'll have to admit that I used it last year as a vapor and had very good results wintering my bees. The "crack pipe" method took a fair amount of time per hive, but I expect with some experience I could speed things up. If you try this method, be really careful about breathing any of the fumes. I know it's been discussed here before, but even a slight wiff gives you that gotta-constantly-clear-my-throat feeling.
I would like to try the drizzle method. It sounds so much simpler and it has a great deal of positive history in parts of Europe.
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