Integrated varroa control in honey bee (Apis mellifera carnica) colonies with or without brood

Abstract

Studies were conducted in two apiaries in order to assess the comparative efficacy of oxalic acid (OA), formic acid (FA) and Thymovar® against varroa mites in honey bee colonies. Treatments were performed using 85% FA, and OA consisted of 2.9% OA dihydrate and 31.9% sugar in water. Consecutive short term FA treatments proceeding Thymovar® application, resulted in an average varroa mortality of 11 and 18% respectively. These varroa mortalities were higher than that in the pre-treatment period (p < 0.05). Mortality rates in FA and OA treated colonies were 42 and 34% of the total mite counts. OA treatment in broodless colonies, after caging the queens for 25 days, reduced the varroa population by 11%. Also consecutive OA sublimations reduced varroa populations by 11, 24, and 16% respectively and the final autumn reduction was 77%. In the second experiment using broodless colonies by caging and isolating the queens, initial OA treatments caused 24% varroa mortality, but three additional autumn OA treatments resulted in 97% varroa efficacy. These studies found that consecutive Thymovar® or OA treatments in colonies with brood have a limited effect on reducing varroa mites. Caging queens to obtain broodless conditions was also not sufficient alone for effectively reducing the varroa mites in colonies during summer months. We conclude, however, that a combination of different treatment protocols, using organic means, can ensure an effective varroa control in colonies.