Comparison of Alternative Application Methods for Anti- Varroa Lithium Chloride Treatments

Abstract

Varroosis is one of the most dangerous threats to the bee industry but means of its treatment are still unsatisfactory. Lithium-based anti-Varroa treatments may provide an alternative, as this trace element can be a natural component of honey and is well tolerated by adult bees. However, it can be toxic to larvae and its use in beekeeping practice is not yet well understood. The present study aimed to investigate the efficacy of relevant application methods of acaricides used in beekeeping practice in brood-free conditions for lithium. Vaporisation proved to be an inefficient method of lithium treatment and killed only 9.9 ± 3.3% (mean ± SD) of mites in the hive. Lithium-impregnated paper strips showed moderate efficiency by killing 55.1 ± 26.2% of mites. The most effective way of applying lithium was the trickling method; different trickling treatments decreased the abundance of mites on average by 65 to 99.7%, depending on the applied dosage and the number of treatments. Repeated trickling treatments were more effective than single treatments, and they generally provided >90% efficiency. Experiments also proved that adding sugar to the trickling solution does not influence treatment efficiency. Thus, it is suggested that repeated and sugar-free trickling treatments with moderate lithium dosage could be the most rational methodology. Since lithium is not yet legalised in beekeeping practice, comprehensive studies are also needed to uncover the amount of lithium residue in bee products, depending on the treatment parameters.

Keywords: Apis mellifera; Varroa destructor; application methods; lithium; trickling.

Figure 1

General linear model analysis considering the influence of the number of mites (covariate) on treatment efficiency via the separate-slopes design revealed significant variation in efficiency (mean ± SD) across eight anti-Varroa LiCl treatment types (for statistics, see Table 3). Plotted values marked with different letters are statistically different at p < 0.05 (Tukey HSD post hoc test).

Figure 2

General linear model analysis considering the influence of the number of mites (covariate) on treatment efficiency via the ANCOVA (homogeneous slope) design revealed that efficiency (mean ± SD) of anti-Varroa LiCl treatments did not vary with the sugar concentration of the trickling solution. In contrast, repeated treatments proved to be more efficient than single treatments (for statistics, see Table 4). Plotted values marked with different letters are statistically different at p < 0.05 (Tukey HSD post hoc test).