Acaricide efficacy and honey bee toxicity of three new formic acid-based products to control <i>Varroa destructor</i>

The replacement of synthetic acaricides with organic treatments is a big challenge in modern beekeeping. In summer 2015, we carried out in Central Italy a study to compare the varroacide efficacy and the toxicity on honey bees of the formic acid evaporator Nassenheider Professional^® with two new formic acid-based gel formulations: MAQS^® and Varterminator^®. In the same apiary with 32 colonies, four homogeneous groups with eight hives each were prepared. The mean acaricide efficacy of Nassenheider Professional^® was 73.2 ± 12.5%, while MAQS^® and Varterminator^® showed a mean efficacy of 49.3 ± 14.9 and 81.2 ± 16.0%, respectively. Colonies showed a statistically significant reduction of adult bees only after the MAQS^® treatment with respect to the control group. All the treatments showed absent or quite moderate queen mortality (MAQS^® and in Varterminator^® groups 12.5%, Nassenheider professional^®, and control groups 0%). Our study indicates that Nassenheider Professional^® and Varterminator^® may represent a sustainable and effective solution to control mite infestation during summer in temperate areas.