This method is also known under the name "thermotreatment".
How does it work?
Varroa mites are more sensitive to heat than bees. Rising the temperature in the hive for a short time can result in varroa kills while bees remain unharmed. Moreover, the intensified abdominal pumping and wing beat activity of the bees in attempt to cool the atmosphere down, knock down the varroa mites.
The bees are confined in a cylindrical chamber where the atmosphere is heated with circulating air at 45-47°C for 10-30 minutes.
Very little documentation is available on this method and there may be variations in the container used (it is sometimes performed directly in the hive), the temperature, the humidity of the blown air, the duration of the treatment and the intervals between treatments.
The efficiency will depend on the conditions of the treatment as described above, but according to Engels, up to 90% varroa kills can be reached.
The method does not eliminate all the varroas and bring a temporary relief only, after which the varroa population may develop again.
According to a beekeeper who uses this method, the bees actually tolerate well a short-time temperature rise: "It is like sauna for us. The bees do not suffer from this treatment; I believe that it even improves their immune system."
It belongs for example to the strategies of Apis mellifera against European wasps and Apis cerana against the Asian predatory wasps to form "heat balls" of up to 46.8°C around hive intruders to kill them by overheating. Bees have therefore actually a capacity to bear higher temperatures for a short time without being harmed.
Nevertheless, experiments of heat treatment on combs have shown to affect the survival of the brood, and treatments made in the spring have resulted in the delay of the development of the hive or even the collapse of the colony. It is therefore recommended to perform hyperthermia treatments in the autumn only.
Due to a remaining number of mites after the treatment, the methods presents the risk of selection of heat-resistant varroa mites, thus that the method may end up to be ineffective.
Reputed as rather laborious, the method requires exact heat and humidity control, which may be difficult with self-made or simple equipment.
Due to the lack of an established and acknowledged method, it is recommendable not trying the method without the exact instruction of an experienced person. The method needs to be tested and refined in order to produce and publish specifications on treatment conditions and equipment.
If the methods is finally developed to an acknowledged technique, vets should be trained to be able perform this method and assist beekeepers.
- ↑ 1.0 1.1 Engels W., 1994: Varroatose - Kontrolle mittels Hyperthermie. Universität Tübingen, Zoologisches Institut, Lehrstuhl Entwicklungsphysiologie. http://www.landwirtschaft-mlr.baden-wuerttemberg.de/servlet/PB/menu/1043468/1043468.html
- ↑ 2.0 2.1 2.2 2.3 Fakhimzadeh K., 2001: Detection of major mite pests of Apis mellifera and development of non-chemical control of varroasis. University of Helsinki, Department of applied biology. http://ethesis.helsinki.fi/julkaisut/maa/selai/vk/fakhimzadeh/detectio.pdf
- ↑ 3.0 3.1 Batz W., 2009: personal conversation with Walter Batz, beekeeper, in 2009-09-29
- ↑ Noirot E., 2000: The Short-Comings of Anti-Varroa Methods. Université de Bruxelles, Laboratoire de psychologie expérimentale. Bruxelles, 2000.http://www.beekeeping.com/articles/us/anti_varroa_methods.pdf
- ↑ Abrol D. P., 2006: Defensive behaviour of Apis cerana against predatory wasps. Division of Entomology, Sher-e-Kashmir University of Agricultural Sciences and Technology, Faculty of Agriculture, Udheywalla Jammu 180 002 (J&K), India. http://www.culturaapicola.com.ar/apuntes/revistaselectronicas/apicultural_science_polonia/50/jas_50_2_2006_5.pdf