Effectiveness of two natural miticides, formic acid and thymol, for control of the mite Varroa destructor in honey bees (Apis mellifera L.) in Villa Guerrero, Mexico

THIS STUDY WAS CONDUCTED TO DETERMINE THE EFFECTIVENESS OF TWO NATURAL MITICIDES, FORMIC ACID AND THYMOL, FOR CONTROLLING INFESTATIONS OF THE MITE VARROA DESTRUCTOR IN HONEY BEE COLONIES (APIS MELLIFERA L.). AN APIARY WITH 36 INFESTED COLONIES WAS ESTABLISHED AND FOUR GROUPS OF NINE COLONIES EACH WERE FORMED. TREATMENTS WERE ASSIGNED RANDOMLY TO THOSE GROUPS AS FOLLOWS: 65% FORMIC ACID (GROUP 1), 12.5 G OF THYMOL PER APPLICATION (GROUP 2), 25 G OF THYMOL PER APPLICATION (GROUP 3), AND CONTROL COLONIES WITHOUT TREATMENT (GROUP 4). AT THE END OF THE EXPERIMENTS, COLONIES WERE TREATED WITH FOUR STRIPS OF A SYNTHETIC MITICIDE (FL UMETHRIN) TO KILL REMAINING MITES AND TO ASSES THE RELATIVE EFFECTIVENESS OF THE TREATMENTS TESTED. THE HIGHEST EFFECTIVENESS WAS OBTAINED WITH TWO APPLICATIONS OF 12.5 G OF THYMOL (92.1%), WHEREAS WITH THE FORMIC ACID THE EFFECTIVENESS WAS 66.4%. BOTH MITICIDES KILLED A SIGNIFICANT NUMBER OF MITES (P < 0.0001), BUT THEIR EFFECTIVENESS DECREASED AFTER THE FIRST APPLICATION. THE TOTAL COST OF TREATING EACH COLONY WAS 70.81, 37.76 AND 70.21 PESOS (6.48, 3.45 AND 6.42 DOLLARS), FOR FORMIC ACID, THYMOL SINGLE CONCENTRATION, AND THYMOL DOUBLE CONCENTRATION, RESPECTIVELY. THESE RESULTS SUGGEST THE USE OF TWO TREATMENTS OF A SINGLE CONCENTRATION OF A THYMOL-BASED PRODUCT (12.5 G).