The effect of different concentrations of oxalic acid in aqueous and sucrose solution on Varroa mites and honey bees

• Published in: Apidologie 2010, Vol.41 (6), p.643-653
• Main Authors: Toomemaa, Kalle, Martin, Ants-Johannes, Williams, Ingrid H.
• Format: Article
• Language: English
• Subjects: Agricultural sciences; Animal biology; Animal production studies; Animal productions; Apiculture; Apis mellifera; Biodiversity; Biological and medical sciences; Biomedical and Life Sciences; Ecology, environment; Entomology; Fundamental and applied biological sciences. Psychology; Insecta; Invertebrate Zoology; Invertebrates; Life Sciences; Original Article; Terrestrial animal productions; Varroa destructor
• ISSN: 0044-8435; 1297-9678
• DOI: 10.1051/apido/2010029

The toxicity of various concentrations of oxalic acid dihydrate (OA) in aqueous and sucrose solution to Varroa destructor and to honey bees ( Apis mellifera ) was assessed using submersion tests of caged bees and by spraying bees in colonies with and without brood. An aqueous solution of 0.5% OA gave effective control of the mite and was non-toxic to bees whereas higher concentrations of OA (1.0–2.0%) were highly toxic to bees. Submersion tests into solutions with 0.1% OA were acaricidal both in aqueous (59.9 ± 3.7 %) and in 50% sucrose solution (71.1 ± 4.2%) whereas concentrations of 0.2–0.5% OA were highly effective; OA in sucrose solution was more toxic to bees than OA in the aqueous solution. Spraying with 0.5% OA solution at a dose of 25 mL per comb in May 2003 and in April 2004 was 99.01–99.42% effective in mite control in Estonian standard one box long beehives with 22 frames (each 414 × 277 mm, area 1000 cm 2 per comb side). Most mites fell after the first spraying. In autumn, spraying test colonies that had little capped brood once or twice with a 0.5% OA solution gave effective mite control (92.94 ± 0.01% and 91.84 ± 0.02%, respectively) with no noticeable toxicity to bees.