Now the last honey must be harvested immediately. We refer you to the last information letter. However, please make absolutely sure that when honey combs are removed from the brood chambers of the productive colonies or even from the young colonies, sufficient honey reserves remain (at least two completely capped combs). In some cases, the colonies are very strong in individual bees and absolutely need these reserves. If you take too much honey from the bees now, you risk that the colonies will starve if replacement feeding does not take place immediately. Please also make sure to complete honey harvesting in the early morning hours to avoid robbing.
Once the honey is harvested, chemical Varroa control must be carried out: As you know, successful beekeeping requires that the Varroa infestation be reduced as much as possible before the rearing of winter bees and that at the beginning of brood rearing in the following year it is at an absolutely low level (=starting population). Temporally, we are now already in the second phase of Varroa reduction. The first phase consisted of regular removal of drone brood during the season and the removal of Varroa mites from the productive colonies through the establishment of young colonies. Only now – after the last honey harvest – may chemical acaricides be used. Varroa control is finally concluded with winter treatment.
The motto is: Whoever does not now skim off a first batch of the existing mites must expect poorly developed winter bees. This significantly increases the risk of winter losses of entire colonies. It is also important to carry out treatment as simultaneously as possible across the area. This can protect against untreated colonies distributing their mites to previously treated neighboring apiaries. When colonies collapse due to Varroosis, most mites are known to be distributed to neighboring colonies through drifting bees or robbing. This objective of treatment as comprehensively as possible across the area is in some places also pursued by veterinary authority general orders. 2 / 3 We recommend in any case carrying out chemical control early this year. Perhaps in this way the Varroa pressure, independent of the infestation of individual apiaries and individual colonies, can be reduced overall across the area.
How can treatment be carried out now? The bee colonies are in brood, so in Lower Saxony essentially one acaricide is suitable – 60% formic acid (FA) ad us. Vet.. This FA can be obtained via the official veterinarian. 85% FA is not approved to date. Only in some federal states can the veterinary authority, due to a treatment emergency, approve the use of 85% FA for a limited time. This does not apply to Lower Saxony. The use of 85% FA is moreover more suitable for the cold season, when 60% FA fails in its effectiveness. Lactic acid (15% ad us. Vet.) can also be used now. However, this does not reach the mites in capped brood and so the treatment must be repeated in any case. Thymol-containing products are apparently not sufficiently effective in this region. Oxalic acid cannot be sufficiently effective at this time of year, since the bees cluster tightly together and the colonies must be brood-free. Application is therefore not advisable at present.
Treatment with 60% formic acid (FA) – short-term treatment We generally recommend the application of FA via the sponge cloth as a short-term treatment. Certainly there are experienced beekeepers who work successfully with long-term evaporator systems. However, since 85% formic acid cannot be used in Lower Saxony, only short-term treatment via sponge cloth remains.
- Preferably cooled 60% formic acid. 2 ml FA per bee-covered DNM/Zander comb
- Outside temperature: between 12 – 25 °C. When daytime temperatures exceed 25 °C, formic acid must be applied in the evening. The weather forecast should be noted, because treatment must not be carried out during thunderstorms, rain, or high humidity. These treatments are ineffective because of moisture-induced dilution of the FA.
- Sponge cloth approx. 20 x 20 x 0.5 cm, apply the acid with a dosing instrument (measuring cup or syringe) only in the middle. For this, the sponge cloth is first placed on an acid-resistant surface (e.g. plate or plastic bowl) outside the bee colony, so that the FA does not drip into the bee colony.
- Before placing the sponge cloth, drive back the bees with smoke puffs and remove wax residue on the top bars with the hive tool.
- Then insert the sponge cloth with the formic acid as close as possible to the bee cluster (on top) and seal it with a plastic sheet against the hive cover
- Any existing screened bottom boards must be covered, but the entrance must be completely open!
- With weak Varroa infestation at least 1 time before feeding, followed by 2 further FA treatments after feeding.
- With strong Varroa infestation 2 applications before and 2 applications after feeding. The time interval between two successive treatments should be approximately 3 to 5 days. You should not reuse the previously used sponge cloth. The already used sponge cloth has too much residual moisture for a follow-up treatment. Let the used sponge cloths dry well first.
- After each treatment (after approximately 24 hours) immediately remove the sponge cloths from the colonies, otherwise the bees will seal and gnaw them.
- Then immediately begin with winter feeding.
Please also observe the safety requirements when handling organic acids. Organic acids are corrosive!
Further details can be found on our homepage at: http://www.laves.niedersachsen.de/live/live.php?navigation_id=20139&article_id=73963&_psmand=23
Dr. Otto Boecking BZB Guido Eich BZB Wulf-Ingo Lau
Lower Saxony State Office for Consumer Protection and Food Safety Institute for Beekeeping Celle – Secretariat Herzogin-Eleonore-Allee 5 D-29221 Celle 05141-90503-40 (telephone) 05141-90503-44 (fax) kathrin.halanke@laves.niedersachsen.de www.laves.niedersachsen.de