Alien species, which are vectors of new pathogens or invasive in nature, can be important factors in ecosystem disturbances. Species affecting bees are given special attention, as they can have serious effects on pollination. In recent years, several invasive species have been identified worldwide.
Invasive Alien Species
Alien species (exotic or non-native), that become invasive or are invasive, were intentionally or unintentionally introduced by human activities. Intercontinental trade of bees is, for example, a potential vector of invasive alien species. These species can affect the native species in various ways: by devouring them, by contaminating them with pathogens, competing with them for resources and habitats or breeding with them.
• The Asian hornet
The Asian hornet, Vespa velutina or yellow-leg hornet, is a species native to South-east Asia. Discovered in France in 2004, it has since become acclimatised to thirteen departments in the South-west. The Asian hornet advanced by 100 km per year and has already been noticed in Belgium. It is a predator of the honeybee. Carnivore, it enters the beehives and eats the bees causing considerable damage. Our honey bee, Apis mellifera, has no defence strategy against this Hornet, unlike the bee-species from South-east Asia. The Asian hornet is closely monitored by the scientific community and by beekeepers. Prevention and control strategies are being developed.
• The small hive beetle
Aethina tumida, its scientific name, is black in colour and is native to South Africa. It parasites the African bee colonies but they are able to defend themselves. The small hive beetle made its first appearance in the United States in 1996 and has since spread across the North American continent. It has also hit Australia. In these regions, the effects on hives can be devastating: the female deposits her eggs in the hive cracks and then the larvae penetrate the cell walls and feed on their contents. Europe has so far been spared.
• Apocephalus borealis
The University of San Francisco has detected a parasitic fly which makes the honeybees leave their hives, disorients them and causes their death. Until now Apocephalus borealis was found only in California and South Dakota, but it could spread to the North American continent. This parasite is a potential vector or a reservoir of pathogens for bees. It has not yet been seen in Europe.
Alien, non-invasive species, may still pose a risk in carrying pathogens. The example of varroa illustrates this risk. In order to produce more honey, the beekeepers of South-east Asia imported colonies of Apis mellifera. These bees cohabited with local honeybee species, Apis cerana. This cohabitation enabled the mites carrying varroa to parasite the Apis mellifera. Transhumance and world trade of swarms have facilitated and accelerated the spread of the parasite in the European continent, where it has been present since the 1980s. Today, the varroa carrying mites have spread almost throughout the globe. Other pathogens could spread this way.