The bee Apis mellifica, otherwise known as the honey bee, is being damaged by a highly invasive parasite Varroa destructor. It is a parasitic mite which comes from the Asia region. The Asia-local east bee Apis cerana is, due to long term co-evolution with this mite, genetically equipped with a regulation mechanism, by the help of which it decreases mite population in the colony on the level which will not cause the colony to perish. In contrast, the honey bee does not have any natural striking power against this new coming mite. At present, the mite Varroa presents a significant and difficult to solve problem for rearing of honey bees. Varroatosis (the disease caused by Varroa destructor) endangers colonies worldwide, although it has not spread in Australia yet. Varroatosis is therefore considered as a globally spread and the most severe disease of bee brood and adult bees.
All development stages of Varroa prey on haemolymph, thus on blood of bees and brood. They do not only deplete the body of the hosts of nutrients but also cause losses of haemolymph through numerous injuries of the skin. Varroa moreover also transmits causative organisms of many serious viral infections of the bees, and without a treatment from human side causes death of invaded colonies in two to three years from their colonization. Weakening of the colonies causes winter colony loss and enables more malign course of many other bee diseases.
The development cycle of Varroa destructor takes place in the honey bee on a sealed brood of worker bees and drones. Just before the sealing, a fertilized female Varroa passes from adult bees to bee brood. After the sealing, she lays on an erect larva and prepupa most often 2-5 eggs. From the egg emerges hexapod larva, next stages are protonymph and deuteronymph. Sexually mature Varroa males develop in seven days and sexually mature females develop in 9 days. While the bees and parasites are still in the cell, male parasites perish after mating and fertilized females take hold of the young bee, finishing the development. Together with the bee, the female Varroa leave the cell. On worker bees or drones they live several days (2-60), before they are sated, move back to cells, and start to lay eggs. For drone bees, it is characteristic for them to drift into other hives and thus they become main transmitters of this parasite. Similarly, worker bees transmit attached mites into surrounding colonies during drifting or robbery.
There are several different methods and procedures currently used for reduction of the quantity of Varroa mite population in bee colonies. The first of them is a method of chemical treatment with substances of an artificial origin. Thus these are substances which are not naturally in nature and are produced by chemical industry. These are, for example, fumigation or contact acaricides. A disadvantage of this treatment, by these substances, is the fact that they may accumulate to human toxic levels in bee products such as in honey and wax. The market value of these commodities is decreased in comparison with the same products from ecological production without toxic substances. Additionally, the mites have already developed an undesired resistance to some remedies.
The second method of treatment of Varroatosis is based on an application of so called “natural chemistry”. This means a treatment with chemical substances, which are ordinarily common in nature. These are, for example, substances which contain formic acid, essential oils, lactic acid, alcohol or traps with aromatic substances, so called pheromone traps. A disadvantage of use of these substances is possible residua, thus remains of more or less poisonous matters that decompose with difficulty. Another disadvantage of this treatment is the fact that the preparations based on organic acids may harm development of the brood and shorten length of life of adult bees. When they are applied, there are problems with their low or short time efficiency. These substances moreover do not, in sufficient amount, affect development stages of mite, covered under wax caps of the cells. Thus, it is very common supplement treatment with application of synthetic matters in form of fumigation, aerosol treatment, insertion of acaricide strips with long term efficiency, spring painting of the brood and so on. These methods of chemical treatment compensate for insufficient efficiency of the substances based on natural chemistry.
The next method of decreasing the amount of mites is biotechnical methods when chemical substances are not used at all. As an example of this biotechnical procedure, it is possible to mention a method of drone brood comb use as an allurement for mite females. This method, however, can be purposeful only at certain periods of the year, generally from April till July when the drone comb is present. Problems with this method include a relatively high work demand factor and a necessity of accurate keeping of terms of cut out and removal of parasitized drone brood. Moreover, according to some studies, cut out of the drone brood decreases honey yield up to 30% and likewise supports swarming of bees.
Biophysical mechanisms are also used for reduction or liquidation of mites in colony. Part of this category is also a method of thermal treatment of colonies. It is matter of common knowledge that even a relatively small increase of the temperature above normal brood temperature, which ranges in interval from 33-36° C., harms mites or even causes their death. Also Indian bees, as an original host species of Varroa mite, purposely warms its worker brood more than its drone brood. Thus, in this Asian species, the mites attach only to development stages of drones. Because they do not parasitize on worker bees they do not disturb viability of society as whole.
The method of thermal treatment of colonies against Varroa destructor has not been yet, even around the world, developed to the point to be usable to the larger extent in ordinary bee operations. The thermal treatment of the colonies is, by part of professional public, perceived and classified as an alternative method of treatment, which is completely inefficient or in practice unusable for whole colonies.
In publication Varroatosis (Dr. Friedrich Pohl, Víkend publisher 2008, pg. 55) is mentioned a method of thermal treatment of combs without bees. In research, not in operational, conditions the brood combs are deprived of bees and in a warm up case are heated for a certain time for mites to die but for the bee brood not to be damaged. This technology is suitable only for scientific experiments, since thermal differences are very low and consequences for bees are to be yet explored.
From a thermal effect application on whole colonies point of view it is possible to distinguish two techniques. The first technique is based on several hours' lasting heating of hive environment to lower temperature of 40-42° C., which is demanding on time and technical equipment. The bees are for the whole period of mite extermination closed in the hive and its entrance is closed, or dramatically narrowed. During a several hours of lasting heating it is necessary to ensure oxygen for imprisoned bees in the method not to cool down the hive. Likewise it is necessary to divert produced carbon dioxide without thermal losses. It is necessary to regulate temperature not to exceed dangerous limit and kill the imprisoned bees. Adult bees, that is to say, are only able to endure lower temperatures than treated brood. This requires installment of accurate regulation mechanisms controlled by thermostats. The beekeeper has to be present and check or control activities of all mechanisms supporting the life of closed colonies. To allow hot air to spread from a heat source along all spaces of the hive, it is sometimes necessary to increase a gap between combs and apply a system of hot air forced circulation in the hive, for example by the help of a ventilator. This requires not only further technical devices but also a necessity of colonies' dismounting. Therefore any method, based on particular colonies dismount and longtime heating of each hive by the source of an artificial heat, is expensive, technically demanding and to a large extent, nonutilizable.
A second technique of a research application of thermal treatment is based on very strong but short lasting heating of the hive interior up to more than 50° C., for period of several minutes. A longer time interval of this strong heating would kill the bees. A disadvantage of this technique is a fact that a thermal effect will not strike mites on brood, because in a few minutes does not come to necessary heating of the core of the combs. The development stages of the mite survive, and only mites which are on bees in the given moment of treatment are killed. Approximately 80% of all mites in the colony are hidden on the brood, however, under protection of a wax cap. Therefore this method is not and cannot be sufficiently efficient in practice as it does not liquidate a majority of parasites. This method is also risky. If the colony is exposed to high temperature several minutes longer than it is optimal it may cause the bee larvae to fall out from the cells of the combs, it may disturb bee brood development or may even cause older bees to perish. The result may be worse consequences for the colony than damage caused by the mite itself.
Different devices for a thermal treatment of bees against Varroatosis are known. For instance in file CZ 235489 is described a solution where a heat exchanger is placed on the bottom of the box and in an upper part are situated controllable openings for hot air off take from the box. Further is known a solution mentioned in file WO2012108857 A1, where in an interior of a hive above a brood area is placed a ridge body connected via a cable to a source of electric current, which in combination with a heat radiator, electronic control unit, thermal sensor, and an optional diagnostic system enables reduction and control of Varroatosis in colonies. GR1005196 B2 introduces a method and a device designed for a thermal treatment of a colony. In this disclosed method, a bee population in a hive is for a period of 12 minutes exposed to temperature of 40° centigrade. A turbine and a pipeline to a bottom of the hive are used to form a hot air flow closed circuit in the hive.
The problem of the majority of so far published solutions is in a limited possibility of their practical use. A thermal treatment is usually not applied on a whole colony, but many devices are based on a bee thermal treatment without combs, combs without bees and so on, which is very labored and in principle nonutilizable in a commercial practice where the beekeeper has to take care of hundreds or thousands of colonies. To reach an effect of thermal killing of mites there are used structurally complicated and thus also expensive devices, dependent on external sources of electric energy. These have movable and therefore faulty parts which wear out when used. This alone complicates their use in a beekeeping profession.
Likewise are known technical designs and techniques which are applicable for whole colonies. For example in magazine “V{hacek over (c)}ela{hacek over (r)}ství” 7/2012, page 231 is described a device for mite liquidation which works on the presumption that the mite dies at 40° C. temperature, but the bee survives for short periods at 50 to 55° C. temperature. A disadvantage of this solution is an excess of labor and a low efficiency, also the fact that a whole colony is inserted into thenno boxes equipped with thermostats treated with a same regulated temperature, whereas adult bees are only able to endure far lower temperatures than young bees, larvae and pupae. If we imprison an entire colony in a hive and heat the hive intensively there is a risk of killing old bees. There is also risk of a suffocation of a whole colony if there is not, by a technically difficult way, ensured an oxygen entry and carbon dioxide take off and this all without thermal losses which would decrease heating efficiency. Devices which would be able to treat whole colonies in a safe way via an accurately regulated temperature and without bees' mortality are therefore very expensive.
The colonies themselves have to, in a brood rearing period, keep temperature of at least 33° C., namely at the expense of metabolic burning of glycide reserves, thus honey and sugar. The temperature has a completely essential importance for a spring development of colonies. It is, for example, known that in urban areas the colonies have a faster development than the colonies in an open countryside by several weeks. This is due to fact that an urban climate is of mere 2-3° C. warmer than in an open countryside. Commonly used hives are not equipped with a device which would generate a thermal energy and thereby simplify and hasten development of colonies in springtime. They also do not have a device which would supply important water in early spring. Therefore, artificially warmed bees fly out from a hive and chill by watering places. A combination of these unfavorable facts decreases honey yield form early flowering cultures and also decreases flying activity and a pollination performance of colonies.
From U.S. Pat. No. 4,494,528 A is known a method of a thermal treatment of colonies which uses a solar energy. A movable solar collector is possible to set in two positions, when in first position the solar collector is placed above the hive and in second position it is inclined in a sunward direction. In this position the hive is heated via solar energy. The cold air is sucked from an interior of the hive into a piping system, is heated by the help of a collector and then it is returned hack to the hive. A disadvantage of this solution is the solar panel must be manipulated at the start and finish of solar heating, which is labor and time demanding.
The aim of a featured invention is to introduce a new method of a thermal treatment of colonies which efficiently decreases Varroa destructor populations' multitude without chemical treatment. The second positive effect is an improvement of thermal wellbeing of colonies and their better development in a spring period. By the help of this invention is significantly reduced an occurrence of parasites Varroa in all development stages, yet it does not achieve 100% efficiency after first treatment. The full extermination of the parasite is reached after repeated use of thermal treatment in a given year. Because the whole colony is not treated at the same time in one step it is not necessary to imprison adult bees, which are high temperature sensitive, in the hive. There is therefore no risk of their killing by a heat during treatment. Therefore there is no necessity of an expensive thermoregulation mechanisms' application. Individual adult bees' age-related heat tolerance is respected by allowing for a possibility of a spontaneous departure of adult bees from the area with, for them, dangerous temperature. Bee brood, which is a highly resistant to temperature, survives thermal treatment without consequences. However the brood is completely free of parasitic mites which reproduce on it. The lifecycle of this device for a thermal treatment is at least as long as a lifecycle of the hive, thus several decades.