Formic acid-based treatment for control of Varroa destructor in a Mediterranean Area

Two formic acid autumnal treatments, gel packets (BeeVar formulation) and impreg- nated paperwick (Liebig-Dispenser), were tested in apiary to evaluate their effectiveness against Varroa destructor Anderson & Trueman and their residues in honey in a Mediterranean region (Sardinia, Italy). Both treatments were efÞcient in the apiary control of the varroosis, with values of percentage of mite mortality ranging between 93.6 and 100%, without statistical differences between them. The more gradual release of formic acid from the gel application allowed a longer action (2 wk for each treatment) compared with the Liebig-Dispenser ( 3 d for each treatment). The rate of daily evaporation ranged between 5 and 9 g/d from BeeVar and 26 and 35 g/d from the Liebig-Dispenser, in the Þrst and second treatment, respectively. The total amount of formic acid administered per hive during all the treatment period was 200 g for either treatment. A signiÞcantly higher adult bee mortality was recorded in the Liebig-Dispenser-treated hives compared with the BeeVar-treated group. On the contrary, BeeVar treatment produced an interruption of brood reared, whereas the extension of the sealed brood area of the Liebig-Dispenser-treated hives was not signiÞcantly different from that of the control hives. Neither queen mortality nor robbing activity was observed due to the treatments. Formic acid residues in honey collected in the nest were 3,855 2,061 and 3,030 1,624 mg/kg for the BeeVar- and the Liebig-Dispenser-treated hives, respectively. After 21 d from the end of the treatment, the residues fell to 1,261 1,054 and 794 518 mg/kg for the honey sampled from the BeeVar and Liebig-Dispenser groups, respectively.