Biomarkers of nutritional status in honeybee haemolymph: effects of different biotechnical approaches for Varroa destructor treatment and wintering phase

Oxalic acid achieves its maximum efficacy against Varroa destructor during the active season only when coupled with brood manipulation techniques like brood interruption and brood removal. This study aimed to assess the impact of these manipulations on the colony nutritional status and the subsequent wintering phase, focusing on selected haemolymph biomarkers: total proteins (TP), zinc (Zn), vitellogenin (VG) and apolipophorin (APO). Twenty-five days after the manipulations (T1), colonies that underwent brood interruption (BI) stored more TP and VG than colonies in the brood removal group (BR), with a lower APO percentage, suggesting a lower metabolic effort in summer. In winter, honeybee colonies of all groups reached similar concentrations of the above-mentioned parameters, but colonies in the BI group showed a higher population. TP, VG and APO are shown to be promising biomarkers of nutritional status of the colony. Basing on the results obtained, we suggest brood interruption coupled with oxalic acid as the preferred organic method for the control of V. destructor in summer.