David Eyre reported a specially strong tobacco smoke used in Europe to knock
down varroa.
This technique was used to detect varroa in colonies in the UK before
Bayvarol strips were approved for use. The problem was that the amount of
smoke needed to give a good effect on varroa also left a good-sized pile of
bees on the hive floor. Most of the bees recovered, but the method seemed to
be a bit severe! Once Bayvarol (and now Apistan) were approved the method
seems to have fallen out of use.

John Burgess, Editor Gwenynwyr Cymru/The Welsh Beekeeper
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If you don't change direction, you'll end up where you're going.