Honeybees are very important pollinators, and are the primary pollinator for many plants. Without honeybees, these plants have greatly reduced fertility. In North America and Australia, where there are no native bee species with large colonies, honeybees can have especially strong effects on native flowers, and on other pollinators such as solitary bee species. Honeybees ability to recruit fellow workers by “dancing” allows them to be more efficient than other pollinators at exploiting patches of flowers. This can create strong impacts on their competitors, especially solitary bees.
Like all social insects, honeybees are hosts to a variety of parasites, commensal organisms, and pathogenic microbes. Some of these can be serious problems for apiculture, and have been studied intensively. At least 18 types of viruses have been found to cause disease in bees, including Sacbrood disease. Several of them (but not sacbrood virus) are associated with parasitic mites. Bacteria infect bees, notably Bacillus larvae, agent of American Foulbrood disease, and Melissococcus pluton, agent of European Foulbrood. Fungi grow in bee hives, and Ascosphaera apis can cause Chalkbrood disease. One of the most common diseases in domesticated hives is Nosema disease, caused by a protozoan, Nosema apis. An amoeba, Malphigamoeba mellificae, also causes disease in honeybees.
In recent decades, two mite species have spread through domesticated and feral honeybee populations around the world. Acarapis woodi is a small mite species that lives in the tracheae of adult bees and feeds on bee hemolymph. It was first discovered in Europe, but its origin is unknown. Infestations of these mites weaken bees, and in cold climates, whole colonies may fail when the bees are confined in the hive during the winter. A much worse threat is Varroa destructor. This might evolved on an Asian honeybee, Apis cerana, but switched on to Apis mellifera colonies that were set up in east Asia. It has since spread all around the world, except Australia. Juvenile mites feed on bee larvae and pupae, and adult female mites feed and disperse on adult workers. This mite is known to spread several viruses as well. Infestations of V. destructor often wipe out colonies. Nearly all the feral, untended honeybee colonies in North American are believed to have been wiped out by mite infestations, along with a large proportion of domesticated colonies. Other mite species are known from honeybee colonies, but they are not considered harmful.
Another commensal or parasitic species is Braula coeca, the bee louse. Despite the common name, this is actually a wingless fly, that apparently feeds by intercepting food being transferred from one bee to another.
Beetles in the genera Hylostoma and Aethina are found in African honeybee nests, where they seem to do little harm. However, the "small hive beetle", Aethina tumida, has become a significant problem in European and North American hives. The larvae eat all the contents of comb: honey, pollen, and bee eggs and larvae. (Adjare, 1990; Roubik, 1989; Sammataro and Avitabile, 1998)