I'm beekeeper from Poland.
"Bee Vital Hive Clean" is popular in my country.
Paper in bottom board after using BVHC in my opinion is similar to paper after application lemon juice+sugar.
I observed it also activates the cleaning instinct of the bees.
0,5 litre natural lemon juice + 0.5 litre sugar syrup (1:1) = 1 litre mixture
application: dribbling 50ml per hive (one box)
varroa drop week after application
I made 2.11 (no brood) experiment with lemon juice and control efficiency 9.11 with amitraz fumigation.
Efficiency more 90%.
Hive1 (buckfast) Hive2(carnica)
lemon juice mixture
2.11 6 2
3.11 28 22
4.11 20 16
5.11 13 8
6.11 8 2
7.11 5 1
8.11 3 1
9.11 1 0
suma 84 52
10.11 12 4
total drop 96 56
efficiency 84/96=88% 52/56=93%
mean efficiency 90.5%
Lemon Juice Mixture:
0,5l natural lemon juice +0,5l sugar syrup 50%= 1litre mixture per 20 hives, application dribbling method 50ml per hive (one box dadant-blatt) or 5ml per comb, mixture must be lukewarm and fresh
Now we (I and my friends in Poland) made big experiment with lemon juice (more 100 colonies), control in december dribbling oxalic acid.
I think, this is very simply, not harmful to bees, ecological method and also surprisingly effective.
In my opinion it work not only chemical ,it also activates the cleaning instinct of the bees.
In next year I will made multiple application lemon juice for yearlong controlling varroa.