Varroa Treatment: The Cornerstone of Modern Beekeeping
Varroa treatment is the most important task of the beekeeping year. Without regular treatment, every colony collapses within a few years.
Why treat at all?
Varroa destructor weakens bees by feeding mainly on their fat body (not on their hemolymph, as was long assumed), and in doing so transmits viruses that deform wings and bodies. Infestation pressure rises exponentially – by autumn, a colony can be carrying thousands of mites.
The three main methods
Oxalic acid (winter)
Application: according to the approval only in the broodless period (late autumn/winter) and only once – in October many colonies still have brood. According to the BVL, honey may only be harvested again the following spring.
- As a trickling treatment (3.5% oxalic acid, 5 ml per bee space) or by vaporization
- No residues in the honey when applied correctly
- Apply only once per broodless phase
Formic acid (summer)
Application: after the last honey harvest, July to September.
- The only method that also works inside capped brood
- Works best at an outdoor temperature of 15–25 °C
- With a suitable evaporator – according to the BVL standard approval evenly over 10 days; for ready-made products follow the package leaflet
- According to the Celle bee institute, treat at outdoor temperatures of 15–25 °C, and above 25 °C only in the evening
Lactic acid (broodless colonies only)
- Manual treatment of individual combs
- Labor-intensive, but well suited to splits and small colonies
- Only on broodless colonies (splits, swarms, winter rest); it doesn't reach mites inside capped brood
Treatment calendar
| Period | Method |
|---|---|
| July/August | Formic acid after the harvest |
| Late autumn/winter | Oxalic acid, once, broodless only |
| Broodless splits and swarms | Lactic acid |
Protection when handling acids
- According to the LWG, oxalic acid is very toxic and can be absorbed through the skin: wear acid-resistant gloves, safety goggles and beekeeping protective clothing, then wash hands and equipment.
- According to the BVL, formic acid causes chemical burns; do not inhale the vapours, wear protective gloves. Do not use during a honey flow, only after the last honey harvest of the year.
- According to the BVL, lactic acid can irritate skin and eyes, and the spray mist can trigger coughing and asthma attacks: wear gloves, safety goggles and a half mask with filter. After a summer treatment, only harvest the following year’s honey.
- Only use the products as the approval or package leaflet specifies – no higher doses and no repeat treatments on your own initiative.
Sources
- Federal Office of Consumer Protection and Food Safety (BVL): Standardzulassung Oxalsäuredihydrat-Lösung 3,5 % (2669.99.99), accessed 5 Oct 2026
- Federal Office of Consumer Protection and Food Safety (BVL): Standardzulassung Ameisensäure 60 % ad us. vet. (2469.99.99), accessed 5 Oct 2026
- Federal Office of Consumer Protection and Food Safety (BVL): Standardzulassung Milchsäure 15 % (2569.99.99), accessed 5 Oct 2026
- Bavarian State Institute for Viticulture and Horticulture (LWG), Institute for Bee Research: Träufelbehandlung mit Oxalsäure, accessed 5 Oct 2026
- LAVES – Institute for Apiculture Celle: Varroa-Sommerbehandlung (Bieneninstitut Celle informiert Nr. 62), as of Jul 2013, accessed 5 Oct 2026
The sources support individual statements in this article. The organisations named have neither reviewed nor endorsed it.