Effect of 0.5, 1.0, 1.5 and 2.0% oxalic acid dihydrate (OA) in aqueous solution on Varroa mites and bees in submersion tests (n = 10 experimental series) at the end of July 2002. Data are presented as means ± standard errors. Concentrations of 0.5–2.0% had similar toxicity to the mites. The 0.5% concentration showed little toxicity to bees but toxicity to bees increased considerably with concentrations higher than 1.0% OA.