Do I need other medications besides formic acid to control Varroa mites?

No, two treatments with the NASSENHEIDER evaporator and 60% formic acid are sufficient to keep the mites below the damage limit. The treatments are carried out in July / August and in September for at least 10 to 14 days each.
Only in case of heavy infestation or reinfection a third treatment is to be carried out in October. This treatment is only possible with the products NASSENHEIDER PROFESSIONAL and UNIVERSAL!
In addition to the treatment with the NASSENHEIDER evaporator, you should only minimize the varroa reproduction by regularly cutting out the drone brood.
For more details, see our instructions for use.

Can I use 85% formic acid for varroa control?

Legal situation in Germany: Varroa control with 85% formic acid is currently not approved.
If none of the approved medications for late-harvest areas is sufficiently effective, there is a therapeutic emergency within the meaning of the German Medicines Act. The situation can be alleviated by the use of 85% formic acid, as it exhibits significantly faster de-milting and higher efficacy at lower temperatures.
The therapeutic emergency is given if the necessary medicinal supply of the bee colonies is seriously endangered and the application of suitable approved medicinal products cannot provide relief.
Please inform yourself at your responsible veterinarian - there is prescription and documentation obligation!
A standard approval as a bee medicine is currently being worked on.

I have 85% formic acid, can I use this for the NASSENHEIDER evaporator or how do I dilute it down to 60%?

We generally recommend using 60% acid for use with our evaporator. All (excellent) test results have been obtained with 60% formic acid.
The acid can be easily diluted:
1000 ml of 85% formic acid + 417 ml of water (can be tap water) yields 1417 ml of 60% formic acid.
When doing this, please be sure to pour the acid into the water, not the other way around!
In addition, please use appropriate protective clothing (rubber apron, rubber gloves, safety goggles)!

Is the NASSENHEIDER evaporator legally approved?

Yes, it is approved by law in Germany (as the only formic acid evaporator of its kind) and in Austria. The approval in New Zealand is already in progress.
Here you can download the Federal Law Gazette in which the German approval was published (in German):

Bundesgesetzblatt Nr. 31, Teil I vom 11.07.2000

Anlage zur Achten Verordnung zur Änderung der Verordnung über Standardzulassungen von Arzneimitteln (auszugsweise Wiedergabe)

Standardzulassung der Ameisensäure 2469.99.99

Can I count on public subsidies for the purchase of the NASSENHEIDER evaporator?

Yes, the animal health insurance funds in some German federal states (e.g. Saxony, Saxony-Anhalt, Thuringia) have made it possible to purchase the NASSENHEIDER evaporator free of charge or at a reduced price since 2000. Since the practice is handled differently in each federal state, we ask you to inquire with your official veterinarian or your animal disease insurance fund.

Do I have to observe the so-called " VARROA WEATHER"?

No, our NASSENHEIDER evaporators PROFESSIONAL and UNIVERSAL adapt independently to changing weather due to their patented 2-fold wicking system. They therefore function at daily maximum temperatures of 10°C-35°C. However, special caution is required at daily maximum temperatures above 30°C to 35°C: use the smallest U-wick (size 1) and observe the behavior of the colonies. If in doubt, remove the evaporator over the heat period.
With the NASSENHEIDER evaporator CLASSIC / CLASSIC II it is important that a sufficiently large brood nest is present, in whose proximity this evaporator must be hung up - the outside temperature does not play a role. Do not use these evaporators at daily maximum temperatures above 35°C.
The "Varroa weather" prediction was invented because there are other, obsolete evaporators that work only in a narrow temperature and humidity range.

How does the formic acid work against Varroa mites - especially with the NASSENHEIDER evaporators PROFESSIONAL and UNIVERSAL?

The amount of AS to be evaporated daily depends on the fact that the gas pressure of the formic acid is so high that the tracheas of the Varroa mites are cauterized and thus killed. The necessary amount of evaporation per hive was also based on several criteria:

  1. the size of the hive
  2. wood or plastic, wooden hives take up more formic acid
  3. very important, the wafting of the bees. Large strong colonies waft more than smaller ones, the bee breeds are also decisive.
  4. the weather: if it is very warm, the bees have to waft more, the gas pressure is lower. If it is cool, there is less wafting, more formic acid remains in the hive. This means, for example, that more acid must evaporate in the summer than in the fall. For this reason we have designed the 3 different wick sizes for the NASSENHEIDER evaporator UNIVERSAL and PROFESSIONAL.

The beekeeper must also contribute something during the treatment, namely check the evaporation amount after 1 and 2 days and possibly change the U wick size. According to the experiments of Dr. Rademacher et al from the Free University of Berlin, the evaporation amount should be min. 6 - 10 ml in autumn and 12 - 20 ml in summer per frame and day. The higher dosage recommendation in summer is primarily due to the faster fanning out of the acid vapors from the hive at higher temperatures.
On the one hand, the U-wick sizes determine the daily drip rate onto the fleece cloth. In addition, acid evaporates through the surfaces of the U-wick. If it is warm, more formic acid automatically evaporates here. This compensates for the formic acid fanning out of the hive.
These criteria all influence the gas pressure in the hive. Therefore, the intuition of the beekeeper or the bee consultant is required. He must judge whether the gas pressure is sufficient to kill the mites. If the gas pressure is too high, the brood, young bees or even the queen will be damaged.
Bees can tolerate up to 250 times higher AS concentrations (gas pressure) than mites.
Also the NASSENHEIDER evaporator is not a miracle cure. Despite its high mite kill rate, there is still a risk of reinfection. Some beekeeper neighbors do not take it so exactly with the treatment. Therefore, if you still notice an increased mite infestation after the first two treatments, we recommend a final treatment as late in the year as possible with 85% formic acid. Officially, this would be "imminent danger" and therefore the use of 85% acid would be permitted in certain federal states.

What should I bear in mind if I do not use 60% formic acid?

Only the acid concentration 60% formic acid is permitted in Germany.
If you use higher concentrations, e.g. 85%, this is only permitted in Germany to a limited extent in some federal states in the event of "imminent danger".
The size of the wicks is designed for operation with 60% formic acid.
When using formic acid in concentrations >60%, select the smaller U-wick size and fill 25% less into the bottle.
Use higher acid concentrations only in moderately warm weather (in the fall), never in summer treatment above 25°C!
You can also dilute higher percentage acid with water. In doing so, please note: Pour the acid into the water, never vice versa!

What is the difference between formic acid strips or any other evaporator and the NASSENHEIDER system?

Only our system can guarantee continuous flow of acid all day and all night - even at different temperatures and humidity levels.
The key is our patented 2-wick system. The first wick (U-wick) drips a continuous flow of acid onto the second wick (fleece cloth).
There, the acid appears as a wet spot that automatically grows larger as evaporation conditions worsen, such as at lower temperatures. The larger spot has more evaporation surface area and this larger surface area always (at temperatures between 12°C-35°C) ensures evaporation of the acid dripping from the first wick. In the worst case, the large wick (the fleece cloth) is completely wet.
No other evaporator / strip has such a large evaporation surface, which even regulates itself.


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