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/cm 2 . 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.Varroa destructor / bioassay / oxalic acid / citric acid / sucrose / glycerol / synergism

Acute Contact Toxicity of Oxalic Acid to Varroa destructor (Acari: Varroidae) and Their Apis mellifera (Hymenoptera: Apidae) Hosts in Laboratory Bioassays

“…Although OA provides effective control of V. destructor, its mode of action is unknown. Furthermore, only one study has quantiÞed the contact toxicity of OA to V. destructor (Milani 2001), and the contact toxicity of OA to honey bees has not been determined. In short, OA is extensively used without knowing the basic toxicological properties of the compound to V. destructor or A. mellifera.…”

Bee-to-bee contact drives oxalic acid distribution in honey bee colonies

“…These studies do not quantify the chronic toxicity of OA to V. destructor because of the impossibility of sustaining mite populations for long periods of time away from their honey bee hosts. Perhaps the chronic toxicity of OA for phoretic mites in the hive environment is significantly less than the acute toxicity reported by Aliano et al (2006) andMilani (2001).…”

“…Another interpretation is that a portion of the varroa mites exposed to OA experience a drawn-out death. Aliano et al (2006) and Milani (2001) demonstrate that OA has a high acute toxicity to mites in laboratory bioassays. These studies do not quantify the chronic toxicity of OA to V. destructor because of the impossibility of sustaining mite populations for long periods of time away from their honey bee hosts.…”

“…Milani reported that the 24 hour LD 50 (95% CL) (median lethal density) for mites collected from brood was 1.9 (1.49 to 2.36) μg/cm 2 . The results from Aliano et al (2006) and Milani (2001) suggest that OA has a high acute toxicity to mites. Aliano et al (2006) indicate that the high acute toxicity of OA to V. destructor in glass-vial residual bioassays suggests that OA readily kills mites that come in physical contact with the crystals.…”

“…Aliano, naliano@unlserve.unl.edu * Manuscript editor: Peter Rosenkranz They reported that the 24 hour LC 50 (95% CL) for phoretic mites was 5.12 (3.5 to 7.0) μg of OA per 20-mL vial. Milani (2001) quantified the toxicity of OA to V. destructor collected from bee brood. Milani reported that the 24 hour LD 50 (95% CL) (median lethal density) for mites collected from brood was 1.9 (1.49 to 2.36) μg/cm 2 .…”