Contact varroacidal efficacy of lithium citrate and its influence on viral loads, immune parameters and oxidative stress of honey bees in a field experiment

Abstract

With an almost global distribution, Varroa destuctor is the leading cause of weakening and loss of honey bee colonies. New substances are constantly being tested in order to find those that will exhibit high anti-Varroa efficacy at low doses/concentrations, without unwanted effects on bees. Lithium (Li) salts stood out as candidates based on previous research. The aims of this study were to evaluate Li citrate hydrate (Li-cit) for its contact efficacy against Varroa, but also the effect of Li-cit on honey bees by estimating loads of honey bee viruses, expression levels of immune-related genes and genes for antioxidative enzymes and oxidative stress parameters on two sampling occasions, before the treatment and after the treatment. Our experiment was performed on four groups, each consisting of seven colonies. Two groups were treated with the test compound, one receiving 5 mM and the other 10 mM of Li-cit; the third received oxalic acid treatment (OA group) and served as positive control, and the fourth was negative control (C group), treated with 50% w/v pure sucrose-water syrup. Single trickling treatment was applied in all groups. Both tested concentrations of Li-cit, 5 and 10 mM, expressed high varroacidal efficacy, 96.85% and 96.80%, respectively. Load of Chronic Bee Paralysis Virus significantly decreased (p < 0.01) after the treatment in group treated with 5 mM of Li-cit. In OA group, loads of Acute Bee Paralysis Virus and Deformed Wing Virus significantly (p < 0.05) increased, and in C group, loads of all viruses significantly (p < 0.01 or p < 0.001) increased. Transcript levels of genes for abaecin, apidaecin, defensin and vitellogenin were significantly higher (p < 0.05—p < 0.001), while all oxidative stress parameters were significantly lower (p < 0.05—p < 0.001) after the treatment in both groups treated with Li-cit. All presented results along with easy application indicate benefits of topical Li-cit treatment and complete the mosaic of evidence on the advantages of this salt in the control of Varroa.

Effects of Plant-Based Supplement on Oxidative Stress of Honey Bees (Apis mellifera) Infected with Nosema ceranae

“…At the end of the experiment on day 14, an increase in the activity of genes for GST and CAT confirmed that this microsporidium causes overexpression of oxidation-related genes [45]. In our previous study [46], in which the effect of lithium citrate was tested, the expression levels of genes for antioxidant enzymes depended on pathogen load. In contrast to the infected group (I), bees that were infected and supplemented (group IT) had lower gene transcript levels.…”

Genotoxic Potential of Thymol on Honey Bee DNA in the Comet Assay

“…The honey bee A. mellifera is thought to be the most negatively impacted by the honey bee mite V. destructor . The mite, which is present almost everywhere in the world, is the main factor contributing to the decline of honey bee colonies [ 78 ]. Due to its role as a mechanical or biological vector of pathogen microorganisms, notably viruses, with the potential to exacerbate pre-existing infections, and its feeding on the fat body and haemolymph of adult and growing honey bees, Varroa poses major health risks to its hosts.…”

“…Due to its role as a mechanical or biological vector of pathogen microorganisms, notably viruses, with the potential to exacerbate pre-existing infections, and its feeding on the fat body and haemolymph of adult and growing honey bees, Varroa poses major health risks to its hosts. [ 9 , 78 , 79 ]. With this in mind, acaricides, whether synthetic or natural-based, must be used continuously in order to control the mite infestation.…”

Lithium chloride treatments in free flying honey bee colonies: efficacy, brood survival and within colony distribution

“…LiCl is an ideal compound under these circumstances, due to its high e cacy and good tolerability by adult bees (Stanimirovic et al 2021;Ziegelmann et al 2018). Some eld tests with lithium salts have already been performed, however most of them used a repeated dribbling method similar to the application of oxalic acid (Jovanovic et al 2022;Kolics et al 2020b;Kolics et al 2022).…”