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Exotic diseases

The western honeybee occurs world-wide, but is not affected by the same diseases everywhere. Some of these exotic diseases pose a major threat because they can have severe consequences following introduction into the Netherlands. To prevent the introduction of such diseases, rules have been established that regulate the import of bees into Europe and imports between European countries.

The Western honey bee (Apis mellifera) has been spread by humans far beyond its natural range. As a result, the species has come into contact with pests, parasites and diseases that are unrelated to its natural enemies. The Varroa mite is an important example of the potential consequences of this process. In addition, parasites from Africa are known which are not a problem for the local subspecies, but to which the European subspecies of the Western honeybee has little or no resistance.

Two exotic diseases currently form the most acute threat, should they be introduced: the Tropilaelaps mite and the small hive beetle.

Small hive beetle

One of the two exotic diseases that currently form the most acute threat, should they be introduced, is the small hive beetle. The other is the Tropilaelaps mite.

Tropilaelaps mite

The genus Tropilaelaps consists of 4 species: T. clareae, T. koenigerum and the recently described species T. mercedesae and T. thaii. Their original host was the giant honeybee (Apis dorsata), but Tropilaelaps can also occur in colonies of other bee species. Both T. clareae and T. mercedesae have been observed in Europe and they can reproduce in European honeybees (Apis mellifera). Tropilaelaps has not been observed in the Netherlands.

The lifecycle of Tropilaelaps spp. in Apis mellifera colonies is comparable with the lifecycle of Varroa destructor. Under normal conditions, 1-4 adult mites enter the brood, each of which produces 1 to 2 offspring. The mites have a preference for drone brood over worker brood (ratio: 3:1). Equal numbers of males and females are produced. When a young bee emerges, the adult female mites also leave the brood cell. The immature offspring and males remain behind and die. The mites remain on the adult bees for no more than two days before they again enter the brood cell to reproduce.

Importing bees

Bees and bee products are traded extensively world-wide. Globalisation has not left beekeeping unaffected. Bee products such as honey and propolis are produced and traded world-wide, but so are purebred queens. This world-wide movement of bees can also lead to the spread of all kinds of parasites and diseases.

To prevent the introduction of new exotic parasites and diseases, European directives have led to national legislation in the Member States. This legislation focuses especially on two exotic parasites: Aethina tumida (common name: small hive beetle) and Tropilaelaps spp. The Dutch government has named Bijen@wur as the national laboratory that is responsible for the legal monitoring of the import of bee queens.