Improving the Varroa (Varroa destructor) Control Strategy by Brood Treatment with Formic Acid—A Pilot Study on Spring Applications

SIMPLE SUMMARY: The varroa mite control in a natural and sustainable way is critical for beekeeping, taking into account the importance of honey bees for pollination as well as for obtaining clean products. In recent time, new procedures for varroosis treatment in the reproductive phase were developed, which can be applied any time during the active season as they use volatile organic acids, widely accepted for organic beekeeping. Such a procedure consists of brushing the capped brood with formic acid, which is very effective in killing varroa mites but also minimally invasive for honey bee colonies. The importance of varroosis treatments before winter bee rearing is evident and widely accepted, as most of the actual treatments are limited to the late active season applications for different reasons, especially because they are focused on phoretic mites. Having in view the flexibility of the new procedure’s application in the whole period of the active season, we started a pilot study to preliminarily test the effectiveness of spring applications on varroa mite control. The results show significant differences in brood infestation between experimental and control groups, in the same apiary, which gives clear indications that spring applications could be beneficial for improving the varroa control strategies. ABSTRACT: The importance of varroosis control in a natural and sustainable way is crucial for beekeeping, having in view the varroa mite impact on honey bee health. In the last years, we developed a highly effective procedure for treating varroa in capped brood using volatile organic acids. This procedure can be applied at any moment of the active season as it uses organic substances. Taking into account the necessity to drastically reduce the level of varroa infestation in colonies before winter bee rearing, we developed a relatively simple pilot study to preliminarily test the impact of spring treatments on varroa infestation level in brood, to be evaluated in summer when, naturally, the population of mites increases. To test the hypothesis, two experimentally treated groups and a control group were used. The treatment consisted of brushing all capped brood with formic acid of 65% concentration in one and two applications. The obtained results show very significant differences between the treated and control groups in terms of infested cell percentages evaluated in the July–August period. Consequently, the spring treatments could be an important tool in limiting the varroa mite multiplication, but further experiments are necessary to test and adapt them to different local conditions.