t3: causes de mortalité des abeilles
Posted by team_3_3 on October 26, 2004 09:16 AM, in categorie(s):
Team 3: abeillles
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L'avis du secrétaire de la Commission internationale des relations plantes/insects évoquée ci-dessus, Gavin Lewis, sur les causes de mortalité des abeilles
1) il explique l'évolution du varroa
2) Il propose d'autres causes, très variées (autres parasites, facteurs climatiques, défauts génétiques...)
Bee mortality: rather Bee health issue
Originally native to Europe and Africa, the honeybee (Apis mellifera) has been successfully imported to various other parts of the world. In more recent years, however, an increase in bee mortality has been observed. Thousands of colonies of honeybees in Asia, Australia, Europe and North and South America have been affected. International experts, including Dr. Gavin Lewis, secretary of the International Commission for Plant-Bee Relationships believe the problem may be caused by a number of factors and a combination of these factors.
The varroa mite as a possible factor
The Varroa mite (Varroa jacobsoni) is particularly aggressive. Several million bee colonies all over the world have already fallen victim to the mite. The mite affects larvae and adult bees alike and causes serious development disorders. Moreover, it acts as a carrier to introduce pathogens into the beehive – including certain microorganisms (spiroplasms) and viruses (paralysis viruses).
The symptoms observed in affected honey bees in Europe would suggest that the cause of the drop in bee populations is the Varroa mite, together with the secondary viruses it can bring with it.
Spread through international trade in honey bees
The Varroa mite originally came from South East Asia and was discovered in the nest of the Asian honey bee (apis cerana) – its original host – as early as 1904. In the evolution of apis cerana, this bee species developed strategies to keep the parasite under control. In France, scientists first identified the mite in the nests of native bees in 1982. Just one year later the mite had spread from Alsace to the Côte d'Azur. This rapid dispersion is characteristic of the worldwide situation: Within thirty years the varroa mite has spread from South East Asia to Western Europe. This is partly due to international trade in honey bees. The export of queen bees has also resulted in the mite reaching the USA via Japan.
Further factors
Apart from the varroa mite, other pathogens include various bacteria and fungi, viruses and parasites. These develop very quickly in combination with unfavorable weather conditions and can lead to mortality among bee populations. Very severe climatic factors such as extreme cold, heat or humidity are particularly damaging. For example, they can mean that the bees are not able to look for food. The resulting shortage of food weakens the entire colony. Other factors for the susceptibility to disease include genetic defects. These may be either spontaneous or a result of artificial fertilization, and the immune system of the bee population affected can be considerably weakened.
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As an internationally important producer of crop protection products, Bayer CropScience accepts the obligation to support research into the various factors of bee mortality. The company has therefore been in contact for many years with apiculturists and recognized international bee experts.