Varroa mite

Varroa destructor is a type of mite that attacks not only the mature honey bees but also the brood. The Varroa attacks the bees belonging to the Apis Cerna and Apis Melifera type. This mite hangs on the bee's body and feeds on the bee's hemolymph. It has been discovered for the very first time in Germany in 1977 by the researchers of the Oberursel Apiculture Institute. Since then it spread around the world as follows:

1. beginning of the 1960s in USSR and Japan
2. in the 1960s and the 1970s in the Eastern European Countries
3. in 1971 the Varroa Mite attacked the bee colonies in Brazil
4. towards the end of the 1970s it spread in the South American countries
5. in 1980 the Polish apiaries were affected by this disease
6. in 1982 it spread in France
7. in 1984 the Varroa arrived in Spain, Switzerland and Italy
8. in 1987 the Portuguese apiaries were infested by this mite
9. in 1987 it moved across the Ocean and infested the USA apiaries
10. in 1989 it arrives in Canada
11. in 1992 the Varroa Mite was discovered in England too
12. in 2000 it arrive in the North Island of New Zeeland and in 2006 in the South Island
13. in 2007 it infested the bee families living on the Hawaiian Islands

The Jacobson Varroa Mite can be seen without the help of a microscope. It has a length of 1.3 mm and a width of 1.7 mm. The majority of them are females which are covered with short, spiky, brown hair and small light brown hairs. Their body is oval. They have four legs which have sticky soles. The Varro Mite males are smaller and have a round shape with a diameter of 0.8 mm. Their mouth is degenerated and it is not suitable for feeding.

The female Varroa Mite can lay between two and five white eggs in the honeycomb cells or on the bee larva having however a preference for drone larva. It takes eight days for an egg to hatch. The mature Varroa leaves the honeycomb cell with the bee that develops from the respective cell. Before the bee leaves the honeycomb cell the Varroa Mites mate and the males die shortly after this event. This explains why females are predominant within a hive. The female mites live around eight months and during this time they can lay around 37 eggs.

The adult mites attack the brood, the result being twin bees with bent legs and wings and other malformations. It is very difficult for these to live and most of them are incapable of doing any type of work. The incomplete developed bees are immediately removed from the cells by the healthy bees.

If the hive is not massively infested it takes the beekeeper up to two or three years to identify the Varroa Mite. Only when the hive is attacked by 10000 mites is the diseases really obvious. If the family is not given the necessary medication it will be completely destroyed in autumn or during the winter.

The bee colonies that are attacked by the Varroa Mite grow weaker and weaker, they become very restless and they no longer take care of the brood. When the infestation is serious there might be even six to eight mites on a single bee.

It has been observed that even during a powerful mite invasion the bee colonies remain intact if they have drone brood. When there are no more drone larvae, the Varroa Mites attack the worker bees' larvae. This is the moment when medication administration is absolutely necessary or else the family will be completely lost.

In order to make a correct diagnosis it is advisable to examine the bees' dirt which can be collected on swaddles put on the frame grids. However, it is necessary to use grids that have a three mm distance between the bars so as to prevent the bees from throwing out the dead Varroa Mites. The Varroa diagnosis can be also set by putting a white piece of paper at the bottom of the hive and then counting the number of mites that have fallen on it. Another diagnosis method implies the examination of caped drone brood. However, this method is quite time consuming. In order to put a correct diagnosis it is necessary to analyze at least 100 drone nymphs per colony. It is possible to see the brown parasites that grow on the white nymphs.

Treatment

According to the most recent research in the domain the natural biological treatment and prevention methods such as the removal of drone brood are not enough to efficiently reduce a Varroa Mite attack. Therefore, the usage of chemical products is indispensable. However, the substance has to be used with the utmost attention. The chemical substance to be used against mites must have the following characteristics:
1. it must not harm the bees
2. it must lead to a complete extermination of the Varroa Mites
3. it must not leave any type of waste in the honey or bees' wax
4. the beekeeper must be able to manipulate and use it easily

Beekeepers can use miticides in order to get rid of this pest. They have to be applies with the utmost care so as not to contaminate the honey or other hive products that are going to be commercialized and consumed by humans. There are several synthetic chemicals that can be used against Varro Mites. These are: Apistan, Organophospate sold as Coumaphos, Thymol Crystal, Perizine or Bayvarol. It is advisable not to use these medicines during harvest time. Beekeepers can also use natural chemicals in their fight against Varroa. Among these we can enumerate: formic acid, lemon, mint and thyme essential oil, oxalic acid, mineral oil, sugar esters and even powdered sugar.

The Varroa Mites infestation can be limited with the help of nonchemical methods. These do not completely eliminate the mites but at least keep their level low so as not to affect the productivity of the bee family. The removal of the drone brood during summer definitely reduces the number of mites within the hive. However, if the hive is heavily infected this measure is not very efficient.

The heating method was developed by the Eastern European beekeepers. The frames are heated for a period of time in order to kill the mites but not damaging the bees. The method of the perforated bottom board is also used in many apiaries. This method functions on the basis that the mites fall off bees and they have to climb back on another in order to survive. The presence of a screened floor at the bottom of the bee hive prevents the mites reentering the hive. Another advantage of this board is the increased air circulation which determines a reduction of hive condensation throughout the cold season. Beekeepers also practice the method of limited drone brood cells. Through this method it is quite difficult for Varroa mites to infest drone cells. The swarming method is also highly appreciated by beekeepers around the world. Through this method the brood cycle of honey bees is interrupted. The frames infested with Varroa are removed and the queen bee is put for nine days into a comb cage. After nice days the queen is put on another comb. The process is repeated again and again until the number of mites in the hive is drastically reduced.

The method of freezing the drone brood is based on the preference that Varroa mites have for drone brood and larvae. Thus, inside the hive is put a honeycomb frame that determines the queen bee to lay drone eggs. The frame is removed and put into the refrigerator when all the drone cells are capped. Through this method both mites and drones are killed. Since the majority of hives produce too many drones, killing a part of them will not be such a huge tragedy for the hive.

Beekeepers also use the method of excision of drone brood. The bees have the tendency to build the cell combs suitable for drone eggs at the bottom or at the outer margin of the comb. If these parts of the comb are cut out the number of Varroa mites inside the hive will be reduced.

It would be an illusion to think that the Varroa mite can be determined through more intensive methods. However, one might assume that the parasites adjust in time to the bee family and vice-versa. In the majority of countries beekeepers have the responsibility to announce the authorities in charge when their hives are massively invested with Varroa mites.




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