I've also read of some Canadian tests which claimed to debunk that (from memory, the Canadian tests did not mimic the usual methodology of sugar dusting, but they still claimed they had proved it useless)
canadian researches has been ment to professional beekeeping. Even if something works in hobby level, it is not proper to earn money. The percent of professional beekeeping is big.
When we look the dead rate of Canadian colony losses, they are big. However it is reported that formic acid efficacy is 96%. In pratice in 30% of hives it is only 70% and it means death to the colony.
To hobby beekeeper 20% dead rate is great, because he does not undertand the issue. My colony vanished, he says.
I asked from our varroa expert, what is mater with Canadian varroa proplems.
He said that with thymol and formic acid concentration must be so big that some brood die and grass in front of entrance wilts. Then hot spell comes and start kill queens because concentration gos too high. Too carefull, and stuff is not strong enough.
It is difficult find this knowledge from internet. Everything is splended when a researcher makes his works. He is not a looser and he wants to money to next project.
It seems that university researches are not allways honest. Results are great but industry suffers.
And then in forum level..... Varroa group has worked carefully 10 years and they publish the results. Then great self made authorities of forum tells their own facts even if they have not made a single research from issue. I do not mention the names but they are same guys here year after year. their screw mus be loosened in the head.
.and sugar on bottom:
- i got an idea
- great fantastic
- learning curve
- you never know if you do not try
c