Maximizing the efficacy of a thymol based product against the mite Varroa destructor by increasing the air space in the hive.
Marco Lodesani, Cecilia Costa.
Varroa destructor can be controlled quite effectively with thymol based products, although environmental factors such as external temperatures, can influence their evaporation and thereby their effectiveness. In this experiment we evaluated how the air space in a hive influences the efficacy of the thymol based product Apiguard®. Three test groups with different volumes of air above the combs (where Apiguard® is placed) were obtained by using a normal crown board (bee space: 0.65 cm), a bee escape frame board (2.85 cm) and an inverted high crown board (6.65 cm). The overall efficacies of the treatments were 78.3 %, 87.6 % and 92.4 % respectively. The efficacy of the product in the group of hives with the greatest air space was significantly higher compared to the group with the smallest air space (P= 0.027). We also found an inverse relationship between the volume of air and the variability of treatment efficacy, which was lowest in the group with the greatest air space (C.V.= 2.62) and highest in the group with the smallest air space (C.V.= 15.62). Our results suggest that a large air space around Apiguard® ensures a more constant and more complete thymol sublimation that may increase its efficacy and reduce variability among hives.