The importance of honey bees to mankind
Around third of our food supply is mediated by insect pollination of agricultural crops, mostly dominated by honey bees. The annual economic contribution from crop pollination is estimated at 200 billion dollars globally. For example In California, the almond industry alone requires the pollination services of 1.4 million beehives annually yielding 80% of the worldwide almond production with a value of ~5 billion dollars a year.
CCD and the Varroa mite problem
It is more than a decade that beekeepers around the globe experience a significant and abnormal annual beehive colony decline rates of about 30% and more. This abnormal phenomenon, known as the Colony Collapse Disorder (CCD), is characterized by rapid decline of adult bee population until the entire colony completely disappears. During the year spanning April 2015 to April 2016, beekeepers across the United States lost 44% of their honey bee colonies. Different causes such as pathogens, pesticides, loss of habitats, malnutrition and more have been suggested as possible sources for CCD. However an increasing amount of evidence suggests that the global spread of the Varroa mite, a multi virus transmitter bee parasite, has a significant impact on the survival rates of honey bees.
Despite the availability of many anti-Varroa products in the market, the Varroa still considered as the number one threat on the global beekeeping industry and as the main cause for colony weakening and collapse. The global failing in controlling the Varroa disease and the big challenge in coping with it, lies in the tight relation that exist between the reproductive cycle of the Varroa and of the bees.
The Varroa mite life cycle
The Varroa mite can live 1-2 and 6-8 months at summer and winter times respectively and involve a life cycle of two stages. A phoretic stage in which the mites ride on adult bees and feeds from the bee’s blood (hemolymph) and a reproductive stage which occurs only inside the capped brood cells. The reproductive stage start by the invasion of an already mated Varroa female into an open brood cell, 0-15 hours before the cell is capped by the bees. Few days after cell capping, the Varroa lays the first egg (male) followed by several daughter female eggs every 30 hours. The Varroa daughters mates with the male within the capped cell and maturely emerge into the hive space together with the emerging of the new born bee. On average a female mite will successfully manage to go through 3-4 reproduction cycles and for the new emerging daughter mites, the duration in the phoretic stage in between two reproductive cycles ranges between 4.5 to 11 days. The Varroa mites multiply very rapidly. In one reproductive cycle which last for 12-14 days within worker and drone bee caped cells respectively at least 1.45 and 2.2 new female mites emerges in addition to the mother female mite.
Phoretic stage: Varroa on adult bee
Reproductive stage: Varroa on bee larva