Drone surrounded by worker bees. © INRA, MORISON Nicolas

Scientists flying to the rescue of bees

An army of enemies

Bees are not short of bitter enemies. At present, around thirty pathogens, predators and parasites are known to attack their hives. Some of them, probably the most dangerous, come from other countries, and notably Asia. Arriving in Europe without their cohorts of predators and parasites, they have become invasive and uncontrollable.

Updated on 03/24/2017
Published on 05/01/2014

Varroa, the hive destroyer

Varroa jacobsoni, vue ventrale.. © INRA, LE CONTE Yves

Scientists are convinced: Varroa destructor does indeed represent a major threat to European bees. Observed in France for the first time in the early 1980s, this mite feeds off the haemolymph of bees. Thus weakened, with their immune defences diminished, the life expectancy of affected bees is markedly shortened. Worse, Varroa is a fearsome vector for the viruses that affect bees.

The war against Varroa is far from being won. At present, only two synthetic acaricides are available on the market in France, and only one, Apivar, against which the parasite has not yet developed resistance. Biological methods are also available, such as rearing a male brood to which the mites direct themselves en masse. Once concentrated in this brood, the beekeepers can destroy the mites with fire and thus relieve some of the pressure on their bees. This method is effective but is very time-consuming for the beekeeper, so it is not appropriate for professional enterprises.

American foulbrood: a threat to broods

Well known to beekeepers, American foulbrood, a disease caused by a bacterium (Paenibacillus larvae), is highly contagious and a real health concern. Attacking broods, it transforms the larvae into a brown, viscous mass. Severely affected colonies see a rapid drop in their population. Once the infection has declared itself, the beekeeper has few alternatives; because antibiotics are banned in beekeeping, the only solution if the colony is severely affected is its elimination by asphyxiating the bees.

Some biological methods to control American foulbrood are currently under study. For example, it has been noted that certain lipids extracted from pollen exert a strong antibacterial activity which can, at least in vitro, hamper development of the bacterium.

Nosema ceranae: the threat of an Asiatic fungus

In 2006, a group of Spanish researchers discovered a new pest affecting European domestic bees (Apis mellifera), a microscopic fungus from Asia called Nosema ceranae. An intracellular parasite which colonises the bee digestive tract, it causes nosema disease, whose symptoms are a degradation of the intestinal epithelium, a reduction in longevity and disturbances to flight activity. It is currently impossible to protect bees against N. ceranae. Although antibiotic-based treatments exist, their use is banned in France because traces of the medication can be found in honey.

Strangely, N. ceranae is not equally dangerous in all countries. In Spain, bees are extremely vulnerable to the parasite, and numerous colony collapses have been attributed to it. By contrast, in France and northern Europe, hives seem to tolerate its presence. To explain this difference, scientists have advanced two hypotheses: firstly, Spanish honey bees, of the Iberian species, may be particularly susceptible, and secondly, N. ceranae appears to be better adapted to high temperatures.

What is a brood?

All eggs, larvae and nymphs that are protected by nurse bees within the hive.