Activity of oxalic and citric acids on the mite Varroa destructor in laboratory assays

Abstract

The toxicity of oxalic and citric acid to Varroa destructor Anderson and Trueman was studied with a laboratory assay. A contact test was used for the bioassay. Capsules were sprayed with solutions of the acids in a Potter tower and allowed to dry. Slight but significant differences in toxicity of oxalic acid were found among mites from different brood stages; the median lethal density for mites from pupae with white eyes was 1.49 μg/cm2. Citric acid was less toxic than oxalic acid. The addition of sucrose to oxalic acid made the material more hygroscopic and the mortality of the mites increased at 75% R.H. Glycerol showed a similar synergic activity irrespective of relative humidity.