My experiment: 

 varroa drop    
                                       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 

amitraz control 
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 minimum 50ml per hive (one box dadant-blatt) or minimum 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. 
 
best regards
Dominik

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