Table 3 Crisis ‘bee’. Status: imminent problem

In recent years, domesticated honeybees (Apis mellifera) and commercially-reared bumblebees (Bombus terrestris) have become increasingly important in global crop production by enhancing pollination [223], as global agriculture faces the major challenge to maintain food security to feed an ever-increasing human population. The challenge grows bigger by the severe declines suffered by these pollinators due to land use change, causing habitat loss, fragmentation, degradation and resource diversity [224], pesticides [225], introduction of alien species for crop pollination and honey production, causing decline on native pollinators [226], and with these, introduction of bee pests and pathogens [227]. Despite extensive research efforts, no single factor has been identified as the definitive cause of bee colony decline [228, 229], and it is likely that the interaction amongst all these factors constitutes the driver for the bee losses. At global level, however, most managed A. mellifera colonies are infected with the ecto-parasite mite Varroa destructor, while other important bee pathogens (e.g. Nosema spp. and several viruses) display global distributions [227]. This points to the significance of these parasites and pathogens in interacting anywhere in the world with other bee colony decline factors, thus intensifying the problem.

The arrival of the powerful gene editing tool, CRISPR [230], could aid towards the alleviation of the situation, particularly now that we have access to honeybee [231] and bumblebee [232] genomes. Certain bee populations practice ‘hive hygiene’ by removing sick and infested bee larvae, and such populations are less likely to succumb to parasite pathogens [103].

Conclusion: Identification of genes associated with the hygiene behaviour and editing them in less hygienic populations would help enhance health of hives globally.