The in-hive pharmacy

Meadow flowers

I’ve written before on the virtues of leaving your honey bees to over winter on their own honey stores rather than feeding them sugar and now there is mounting scientific evidence to support the view.

Recent studies by a team from Martin Luther University Halle-Wittenburg, Germany¹ found that nurse bees select different honey according to their health needs.  In the hive, honeys from different plant sources are stored in separate cells in the comb.  This means that the nurse bees who feed the larvae and new brood can choose which honey to select and the studies have shown that they do show a preference for particular honey when there is a specific problem.  Bees infected with the fungus Nosema ceranae (Nosema is related to dysentery) showed a significant preference for sunflower honey compared with black locust, linden and honeydew honeys.  Sunflower has the highest antimicrobial effect of the four honeys.

But before we start to think about feeding our bees on specific forage, a study ² carried out at the same university two years later looked at 3 honeys’ action on the bee diseases European foulbrood (EFB) and American foulbrood (AFB), this time in vitro.  Sunflower honey was found to be effective against AFB and black locust against EFB.  However the most effective honey against both was the polyfloral honey³.  The combination proved effective against both pathogens and had double the amount of polyphenol compounds, suggesting the importance of diversity in the bee diet.

Resin collection has also been shown to vary according to the colony’s needs.  In 2012 a study by the University of Minnesota showed that there was a significant  increase in foraging for resin when bees were infected with the chalk brood fungus.  The resin is turned into propolis by the bees which has antimicrobial, antibiotic and antiseptic properties and was shown in the study to decrease the parasite load.

How the bees know what to do is still very much a mystery but seems to fit under the term ‘hive wisdom’.   Not only can they adapt (resin) foraging behaviour according to the health of the colony overall but they can administer their own ‘medicine’.  We don’t know if they will forage for the nectar from a particular plant when there is a particular health problem but once the nectar is stored as honey they can use the stores as an in-hive pharmacy.  This highlights the need for the stores to be well stocked with as diverse a range as possible.  Lack of diversity of flowers in the environment and all year round variety could have a negative impact on their well-being therefore.  Removing honey stores and replacing them with honey made from sugar syrup will mean that the secondary metabolites that contribute to the specific antimicrobial properties of different honeys are missing.

This research sheds light on the potential drawbacks of traditional beekeeping such as routine feeding of sugar to honey bees.  Let’s hope the message filters through to all beekeepers – and rapidly.

 

 

¹ Pathogen-associated self-medication behavior in the honeybee Apis mellifera   Bogdan I. Gherman et al 2014

² Diversity of honey stores and their impact on pathogenic bacteria of the honeybee, Apis mellifera  Silvio Erler et al 2014

³ The melissopalynological analysis of the polyfloral honey showed a mixture of maize (Zea mays), common dandelion (Taraxacum officinale), cornflower (Centaurea cyanus), spiny plumeless thistle (Carduus acanthoides), wild thyme (Thymus serpyllum), common hawthorn (Crataegus monogyna), meadowsweet (Filipendula ulmaria), common sainfoin (Onobrychis viciifolia), rapeseed (Brassica napus) and sunflower (Helianthus annuus) pollen, and honeydew elements of about 10% from the total pollen number.

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