Blog

How understanding the buff-tailed bumblebee could help save the bees

This article, by PhD student Sarah Larragy, first appeared on RTE BRAINSTORM on 27 April 2021

“Save the bees”; This phrase has been meandering through various media platforms and trending hashtags for a while now. But who are these bees? And why should we to save them?

This mirrors a much wider decline in insect populations observed in many regions around the globe. For instance, a 27-year-long study by Hallman et al. (2017) in Germany found that insect biomass had declined by three quarters in this time period. Unfortunately, the suspected culprits of insect pollinator declines are all too familiar: habitat loss, pesticide use, disease spread and climate change.

Most people are aware of the critical link between bees and pollination. About three quarters of crops produced globally require animal pollination to some degree, meaning insect pollinator declines could threaten the food supply of our already crowded planet.

To put a number on this, the recent Pollival report estimated that global pollination services are worth between €260 billion and €1.1 trillion every year.

My research focuses on Bombus terrestris, also known as the buff-tailed bumblebee. It is not an endangered species, but a model-organism for pollinator research, much like mice or Drosophila melanogaster, the common fruit fly. Buff-tailed bumblebees are naturally found across Europe and Northern Africa.

Bombus terrestris, the Buff-Tailed Bumblebee, Dublin. Photo © Jane Stout

Across its range, this species has pocketed itself away in several geographically isolated areas, like Ireland, the Canaries, and Sardinia. Evolution has already caused variances in how this bee acts and looks in many of these places and several of these are classified as unique subspecies.

Buff-tailed bumblebee colonies have also become a commodity; they are grown and exported around the world by commercial companies. In Ireland, these colonies are used to pollinate crops like apples, strawberries, blackberries and cranberries.

Commercial bumblebee colonies in a fruit orchard. Photo © Jane Stout

They are much-loved by growers as bumblebees can forage in our grubby Irish weather and can provide buzz pollination to plants that can’t be pollinated without it.

Although these colonies are a great resource for growers looking for pollination services, it’s possible that they may pose some risks to wild bees, including pathogen spill-over, hybridisation and competition for floral resources.

My PhD research is funded by the Irish Research Council and is based in the Applied Proteomics lab in Maynooth University. In a nutshell, the aim of my research is to characterise the native population Irish buff-tailed bumblebee from the genetic level all the way up to the behavioural.

Sarah Larragy (L) and Merissa Cullen (R), bumblebee researchers in the Applied Proteomics Research Group, Maynooth University

Genetic distinctions can indicate when a population may be on track to diverge from the larger species group and perhaps evolve into a new sub-species or species. Although Ireland is often considered species poor next to Britain & mainland Europe, there are several genetically unique species populations here, such as the native black Irish honeybee rediscovered just a few years ago.

Ireland may host many more distinctively ‘Irish’ species populations. Through whole genome sequencing supported by the Department of Agriculture’s Genetic Resources Grant Aid Scheme, our project team hopes to evaluate the genetic uniqueness of Irish buff-tailed bumblebees.

This is a collaborative project involving my supervisor Dr James Carolan (MU), Prof Jane Stout (TCD) and Dr Joe Colgan (JGU, Mainz). Should we find that Irish buff-tailed bees are a genetic resource, we will need to consider how best we can conserve one of our most important native pollinator bee species.

I plan to evaluate how our Irish buff-tailed bees respond on a molecular level to pathogens and pesticides. We do this by identifying which proteins become up or down-regulated in, for example, haemolymph (the insect equivalent of blood) in response to a stressor. This is called proteomics and can let us know what could be happening on a functional level in the body of the bumblebee.

It’s possible that pollination and foraging efficiency may differ across subpopulations of bees, especially those with different genetic backgrounds or those living in different climatic regimes. I want to assess this behavioural aspect of Irish buff-tailed bumblebees to see how they compare with imported colonies in the Irish environment.

It may be that imported colonies provide excellent pollination services to crops and while they may be necessary to sustain food production, they could compete with our wild bumblebees for pollen and nectar.

I am hoping that my research will show the importance of understanding the diversity within different populations of the same species. I anticipate that this research will shed some light on the risks associated with imported bumblebees and I don’t think it is possible to remove every potential threat to our biodiversity.

Anywhere humans and wildlife co-exist, conflicts of interest are sure to crop up. However, we can try to strike a balance. In this light, I believe my research will lead to evidence-based solutions and management strategies that will help achieve the best of both worlds i.e. getting the best pollination services we can while also reducing any risks posed to wild pollinators.

And, perhaps, this will be one step towards how we will save the bees.

About the Author: Sarah Larragy is a PhD student at Maynooth University, supervised by Jim Carolan and Jane Stout. Her work is funded by the Irish Research Council. She led the development of the All-Ireland Pollinator Plan guidelines for users of imported bumblebee colonies.

My Shea Story

From pollinators to policy – the story of applied ecological research across continents

Back in 2015, I had a blast from the past when a former colleague (we did our PhDs together at Southampton University in the late 1990s) got in touch to ask whether I’d like to work on pollination of shea (Vitellaria paradoxa) in West Africa. I had done very little tropical ecology work, and had to google shea, but said “Sure, why not?”. Before I knew it, I was in Ghana, learning about shea growth, production and markets as part of a team including scientists, international and national NGO workers, and representatives from the shea industry.

Shea “nuts” drying (L), prior to being boiled and processed into Shea butter (R), July 2015

We designed an experiment across six sites in Ghana and southern Burkina Faso, and the following year, I was back setting up the experiment. We did pollinator exclusion trials to test for pollinator dependency, and surveyed which insects were visiting the flowers and actually doing the pollinating. This pilot study showed that the majority of flower visitors to shea (88%) were bees, most frequently small social stingless bees (Hypotrigona gribodoi), but native honey bees (Apis mellifera adansonii) were also common visitors to flowers early in the morning. The number of fruit produced per inflorescence was significantly lower when insects were excluded during flowering by bagging, but any fruits and seeds that were produced in bagged treatments were of similar weight to un-bagged ones. This work was published in the Journal of Pollination Ecology.

The pollination team in Ghana, January 2016

Of course, this study generated as many questions as it delivered answers, and so we sought more funding. Fortunately, we were successful and between 2016 and 2019, we were partners on a U.K government Darwin Initiative funded project researching both the impact of habitat diversity upon pollination services in shea parklands of southern Burkina Faso, and also how farmer led agro-ecological interventions, referred to as the ‘Trees Bees and Birds strategy’ can increase on-farm biodiversity, and improve parkland habitat at landscape level.

This time, I was lucky enough to go back to Burkina Faso with Dr Aoife Delaney, who had just completed her PhD with me. We set up an experiment to compare pollination and fruit production in landscapes with different levels of biodiversity, to try and understand whether in more degraded sites, the shea was adequately pollinated. Aoife stayed in Burkina Faso for six months to complete the field study, working with our local partners and farmers.

We found that in the more biodiverse sites, honey bees were observed more frequently, whereas other bee species were generally widespread, but they did visit trees in greater numbers at diverse sites. We also found that shea fruit production was significantly limited due to lack of pollination and that the degree of pollination limitation was greater in sites with lower levels of tree and shrub diversity. This work was published in Journal of Applied Ecology. See our blogs on The Applied Ecologist and RSPB sites for more.

Aoife Delaney, meeting local partners in Burkina Faso, January 2017

So, the ecological conclusion was to maintain or improve habitat level biodiversity to optimise levels of pollination for shea, and presumably other plants in the Parklands. This biodiversity would then provide multiple benefits to people, including forage and shelter for livestock, firewood, building materials and traditional medicines. The presence of trees helps to bind the soil, reducing organic matter loss, and leguminous tree species in the parklands including acacia and African locust bean improve soil fertility. The populations of insect and bird species helps to provide pollination and pest control functions.

However, these are heavily populated landscapes and increased demand for land under active cultivation has led to more land clearance, shorter fallow periods and smaller fallow areas in the Parkland. With less time and space for natural regeneration to occur, the trees and shrubs in the shea parklands have become less diverse and less abundant. Thus there are trade-offs to be made in land-management, and sustainable solutions need to be found.

To address this issue, together with Elaine Marshall the Project Leader at BirdLife International, we highlighted these issues at a “Lessons Learned” workshop in June 2019 at the David Attenborough Building in Cambridge, focusing on partner-led community conservation approaches around the world, including the Trees Bees and Birds strategy. We summarised the challenges and solutions in terms of tackling ecological restoration as follows..

CHALLENGES:

  1. We need solutions to reverse the drivers of biodiversity decline
  2. Nature appears to be invisible in a lot of decision-making
  3. Loss of biodiversity and ecosystem degradation damages the flows of benefits we get from nature
  4. There are conflicts and trade-offs in ecosystem restoration
  5. Research and education efforts are currently inadequate

SOLUTIONS:

  1. Research and (importantly) knowledge transfer
  2. Facilitation of Indigenous Local Knowledge (ILK) sharing
  3. Target messages and roll out across sectors
  4. Build on international initiatives for restoration and frameworks for accounting for the benefits from nature

And we concluded this was all URGENT…

Jane Stout, Elaine Marshall and Aoife Delaney in Cambridge

And in 2020, we published a Policy Briefing on ” Building Resilient Landscapes and Livelihoods in Burkina Faso’s Shea Parklands” to try and address some of the issues that had been raised during the project. This highlighted the outcomes of our research, and made policy-relevant recommendations. This Briefing can be downloaded below.

And we are continuing to do the research. Latif Nasare, Lecturer at University for Development Studies in Tamale, Ghana, is conducting his PhD on shea pollination, and I’m co-supervising him. He’s investigating patterns of shea flowering phenology, how pollinator abundance varies with climate, the effects of honey bee keeping on shea yields, and forage resources for pollinators outside of the shea blooming period.

Shea flowers being visited by tiny “stingless bees”

Latif is just completing his first field season, and I’m anxiously waiting for news of how he has got on, and for travel restrictions to be lifted so that I can go back to this wonderful part of the world to continue my shea story.

About the Author: Dr Jane Stout is Professor in Botany at Trinity College Dublin, and leads the Plant-Animal Interactions Research Group. She is co-founder of the All-Ireland Pollinator Plan and Natural Capital Ireland.

Irish Pollinator Research Network meeting 2021

Despite the global pandemic, lockdown and geographic dispersion of researchers (who are currently scattered across Ireland, UK, Zambia, Ghana, Italy…), the Irish Pollinator Research Network (IPRN) gathered for its annual research symposium on 20th January 2021. Smoothly organised by TCD postdocs Jordan Chetcuti and Stephanie Maher, the meeting featured 16 presentations, with 26 participants at any one time (not always the same 26!).

The IPRN was established in 2017. Since then, we’ve met at TCD in 2018, DCU in 2019 and MU in 2020.

This year, researchers from TCD, UCD, MU, DCU, NUIG, and NBDC gathered to share research outputs, plans and ideas. Presentations covered a range of topics (listed below with my own personal take-home note!), and there was lively and constructive discussion after each one:

  • modelling bees and their responses to pressures (is difficult because so many parameters to include and we still don’t know enough about basic biology of bees to parameterise models perfectly)
  • how pollinators interact with plants and soil communities (ecological interactions are complicated, and we need to know more about soils and species traits)
  • how bees are affected at a proteomic level by stressors such as pesticides and pathogens (we need to know more about bee immune systems, commercial formulations need more testing, and proteins/pathways have weird names!)
  • analysing pesticide residues in soils, nectar and pollen (chemical extraction methods depend on both the matrix and the analytes of interest)
  • how bees are affected at an individual behavioural and colony level by pesticides and climate (bees don’t always do what you expect in flight cages!)
  • pollinators and pollination of flowering crops in Ireland (landscape surrounding fields/orchards can influence pollinators and pollination services)
  • schemes to promote pollinators on Irish farmland (with relatively little effort, farms can become much more pollinator-friendly)
  • pollination in African woodlands (although many woodland species are valuable to locals, role of pollination is not well understood, and different plant species react differently to pollination).

One thing that was apparent was the huge amount of work that has continued over the past year, despite the pandemic. A massive round of applause for all researchers for continuing to do amazing research despite restrictions, illnesses, constraints and other personal and national traumas…

Another thing that struck me was that there is so much synergy, collaboration and friendship in this network. We are there to support, help and advise each other, not to compete with one another, and that was apparent. This is so refreshing and I am feel very proud and privileged to work in this group. Keep it up everyone and looking forward to gathering at UCD next year!


To find out more about the IRPN members, see links to PIs below:

Jane Stout, TCD: Pollination ecology, plant-pollinator interactions, pollinator diversity and drivers of decline, landscape and agroecology, pollinator conservation, valuing pollinators and pollination services

Dara Stanley, UCD: Plant-pollinator diversity, interactions and conservation, pollinator behavioural ecology, agroecology, impacts of pesticides on bee behaviour and provision of pollination services.

Jim Carolan, NUI Maynooth: Cellular and molecular level effects of various stressors (pathogens, parasites and pesticides) in both native and commercial bees, bumblebee conservation, DNA barcoding and genomics.

Blanaid White, DCU: Analytical chemistry, honey chemistry, pesticide contamination of soils/floral resources.

Grace McCormack, NUI Galway: Disease tolerance/resistance in native Irish honeybees, wild honey bees.

Una Fitzpatrick, National Biodiversity Data Centre: All-Ireland Pollinator Plan

    

About the Author: Jane Stout is a Professor in Botany in the School of Natural Sciences at Trinity College Dublin and leads the Plant-Animal Interactions Research Group. She is co-founder of the All-Ireland Pollinator Plan.

What do insects have to do with eating, drinking and kissing this Christmas?

We don’t see many insects during the winter, but their legacy is evident in terms of the fruits and seeds that they have helped to produce earlier in the year. Without insects, we wouldn’t have many of our Christmas foods, drinks and decorations. This is because many of the plants that produce our Christmas treats rely on insects pollinating flowers earlier in the year.

Without insects, we wouldn’t have bright red holly berries to decorate our Christmas puddings, mistletoe with its characteristic white berries to kiss under, cranberries to liven up our turkey, chocolate, marzipan or many of the spices and other goodies we associate with Christmas.

This is because insects are needed by most plants for cross-pollination, which results in the production of fruits and seeds. Since plants cannot move to find mates themselves, they rely on insects to bring male and female together.

Holly (Ilex aquifolium) is unusual in the plant world because male and female flowers occur on separate shrubs. As bees drink nectar from male flowers, they get pollen on their bodies and when they move to a female plant to continue to feed, they deposit that pollen on female flowers. The pollen causes the female flowers to be fertilized, and to form fruits (or berries) containing the fertilized seeds.

A bumblebee visits a Holly flower in Co. Wicklow in April to drink nectar. (Photo J. Stout)

Similarly, mistletoe (Viscum album) also holds its male and female flowers on separate plants. Plants are partially parasitic and live on the branches of other trees but still rely on insects (not just bees, but also flies, bugs and beetles) for pollination and thus berry production.

In fact, both mistletoe and holly fetch higher prices at market if they have berries on them, and so insect pollinators are of economic value at Christmas time as well.

Cranberry bushes (Vaccinium macrocarpon) produce both the male and female structures not just on the same plant, but in the same flower. However, they still need bees to transfer the pollen between flowers, because those male and female structures do not mature at the same time.  Large bees, such as bumblebees, which can shake the flowers in just the right way to dislodge the pollen (producing a distinctive buzzing sound) are the best pollinators. This is known as “buzz pollination” and is important in other crops too (including tomatoes and blueberries).

Chocolate-producing cocoa trees (Theobroma cacao) produce small flowers on their trunks, and although flowers don’t produce a scent to attract pollinators, they produce a small amount of nectar and are visited and pollinated by tiny flies (midges). Although flowers contain both male and female structures, they cannot fertilize themselves, and these midges are needed for the production of cocoa fruits, which contain the seeds from which we derive chocolate. These trees grow in the tropics and flowers and fruits are produced throughout the year, although it takes 5-6 months for them to mature before they are harvested.

Marzipan (almond paste) is made of ground almonds (and sugar). Almond (Prunus dulcis) trees bloom in early spring and are visited by bees – both managed honeybees and wild bees. In fact, almond trees in California (where most of the world’s almonds are produced) produce better yields when both honeybees and wild bees are present in orchards. This is because they complement each other in their foraging. If there are no bees at all visiting flowers, fruit set can plummet by up to 90%.

Honeybees are important pollinators of almond flowers (Photos J. Stout)

Many of our Christmas spices, including cinnamon (Cinnamomum spp.), cloves (Syzygium aromaticum) and nutmeg (Myristica fragrans), essential ingredients in Christmas cakes, puddings and mulled wine, also need pollinating by insects. In the case of cinnamon and cloves, this is done by bees, but for nutmeg, it’s beetles that do the pollinating job.

So, as you enjoy Christmas this year, raise a glass to the insects that made all of this possible.

For more information on pollinators, their value and conservation, see the All Ireland Pollinator Plan www.pollintors.ie.

Links:

FAO Crop pollination database

Adjaloo & Oduro (2013) Insect assemblage and the pollination system in Cocoa ecosystems. J. Appl. Biosci. 62: 4582 – 4594

Brittain, Williams, Kremen, Klein (2013) Synergistic effects of non-Apis bees and honey bees for pollination services. Proceedings of the Royal Society B-Biological Sciences 280(1754)

MacKenzie (1994) The foraging behaviour of honey bees (Apis mellifera L) and bumble bees (Bombus spp) on cranberry (Vaccinium macrocarpon Ait). Apidologie 25: 375-383

Ollerton, Rouquette, Breeze (2016) Insect pollinators boost the market price of culturally important crops: holly, mistletoe and the spirit of Christmas. Journal of Pollination Ecology 19: 93-97

This article first appeared in The Independent in 2015.

About the Author: Dr Jane Stout is Professor in Botany at Trinity College Dublin and leads the Plant-Animal Interactions Research Group. She is co-founder of the All-Ireland Pollinator Plan.

Honey fraud: The secret behind the labels

By Elena Zioga

Honey is a complex natural product produced by many social insects such as bees (Apinae, Meliponinae, and Bombinae), honey wasps (Polistinae), and honey ants (Formicinae and Dolichoderinae). However, the most important source of honey sold commercially comes from only few of the 20,000 bee species – the honey bees (Apis spp.).

Honey benefits for humans

Honey has been exploited by humans since ancient times, and nowadays is a widely consumed product, appreciated for its taste and its health benefits. It contains a variety of ingredients, such as sugars, amino acids, minerals, enzymes and vitamins, which are beneficial to humans. The main sugars of honey (fructose and glucose) are digested more easily and quickly by the human body compared to other sugar types. In addition, glucose is the only form of sugar that can be used by muscles, so honey is an excellent source of energy for children and athletes. The minerals (potassium, calcium, copper, iron, magnesium, manganese, phosphorus, sodium, zinc and selenium) in honey help the body’s cells function, maintain healthy bones and teeth and prevent blood clotting. The main naturally occurring enzymes in honey (diastase, invertase, and glucose oxidase) enhance the digestion of food substances, especially carbohydrates such as sugars and starch. Also, honey contains many vitamins, such as ascorbic acid (C), thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), and pyridoxine (B6), etc., which contribute to the absorption of sugars by the body and to its proper functioning.

What is honey?

As a natural product, honey, even when it comes from a single hive, varies in terms its physicochemical characteristics. A recent study on Irish honeys demonstrated that the physiochemical properties varied according to floral origin, and whether hives were placed in urban or rural sites. The botanical origin and ripening conditions of honey are the main factors responsible for this variance, affecting its natural properties (e.g. colour, aroma, taste, tendency to granulate or ferment, density, viscosity and fluidity, hygroscopicity), but also its antioxidant and antibacterial action. Thus, by studying all the physicochemical, organoleptic and microscopic characteristics that define a specific honey category, we can assign an identity to honey and evaluate it qualitatively in accordance with the international legislation. It is important for the consumer to know how the quality of honey is determined, and to maintain a good value for money, given the widespread practice of adulteration in imported honeys.

According to the broader definition given by Codex Alimentarius (2001), honey is defined as “the natural sweet substance produced by honey bees from the nectar of plants or from secretions of living parts of plants or excretions of plant sucking insects on the living parts of plants, which the bees collect, transform by combining with specific substances of their own, deposit, dehydrate, store and leave in the honey comb to ripen and mature“. On a European level, the Council Directive (2001/110/EC), defines honey as “the natural sweet substance produced by Apis mellifera bees (“bees”). Honey consists essentially of different sugars, predominantly fructose and glucose, as well as other substances such as organic acids, enzymes and solid particles derived from honey collection“.

Based on those definitions, honey can be divided into two main categories:

  1. Blossom or Nectar honey, produced from the nectar of either one kind of flowers – uni-floral (e.g. oilseed rape, brambles, orange, cotton, sunflower, heather etc), or of the combinations of various kinds of flowers – multi-floral.
  2. Honeydew honey, produced from secretions of living parts of plants or plant sucking insects on the living parts of plants (e.g. honey of pine, fir, oak and other forest plants).

A notable difference occurs between the two honey definitions. While Codex Alimentarius (2001) mentions that honey is produced by “honey bees“, which is more generic term, the European Directive mentions specifically the species “Apis mellifera L.”. This is because A. mellifera is the honey bee species that occurs and is domesticated for honey production in European Union (EU), while other honey bee species may occur and are being exploited for honey production in other parts of the world (e.g. A. cerana in South Asia).

Honey production by the species A. mellifera

A worker honey bee, after emerging from its cell as a mature adult, lives for almost six weeks in the summer, spending the first three weeks of its life inside the hive as a “domestic honey bee”. After this period, she becomes a collector and works the second half of her life outside the hive collecting nectar, pollen and water (Fig. 1). Honey production is the most important work of honey bee collectors. They fly diligently and tirelessly from morning to dusk in all directions and at various heights and distances up to 10 km from the hive in search of plants that produce nectar. When the nectar source is found, the honey bee sucks the nectar from the flower with her proboscis and temporarily stores it in a special receptacle inside her body, called the honey stomach, foregut or crop. To gather a full crop load of nectar, a bee forager may visit up to 1,000 flowers, and may make around 10 trips per day. When the honey stomach is full, the forager honey bee returns to the hive. Upon her return, she adds the enzyme invertase to the collected nectar. This action initiates the process of turning nectar into honey. The enzyme breaks down the sucrose found in nectar into simpler and more digestible sugars for honey bees, which are mainly glucose and fructose. Back in the hive, the honey is delivered to the nurse honey bees, who store it in the honeycomb cells. Once it enters the cells, the water must be evaporated, for the dehydration process to begin. In order to do that, nurse honey bees flutter their wings, dissipating the extra moisture and turning it into honey. Once this process is completed, the nurse honey bees will cover the top of each filled cell with a thin layer of wax and close it airtight for future use.

Figure 1. A forager honey bee (A. mellifera) collecting pollen and nectar from a Cistus sp. plant.

Honey fraud

According to Food and Agriculture Organization of the United Nations (FAO), despite the overall increasing trends in the number of managed western honey bee hives, important seasonal colony losses are known to occur in some European countries and in North America, while data for other regions of the world are largely lacking. On the other hand, honey demand has increased worldwide, due to recognition of its natural medicinal and nutritional properties and its wide range of applications in food industry.

Hence, honey is becoming an increasingly scarce commodity and, as a natural product with a relatively high price, honey is among the top 10 foods with the highest adulteration rate in the European Union. Consumers, often unknowingly, do not receive the natural product they paid for, while adulterated honey found in the market may pose a threat to food safety, food security, and ecological sustainability. A conscious consumer should be aware of the problem of honey fraud and how to get suspicious of it.

The general term “food fraud” can be taken as encompassing a wide variety of activities referred to adopting the wording contained in European Regulation (2017/625) as “fraudulent or deceptive practices” by businesses or individuals for the purpose of gaining some form of undue advantage and/or causing harm. The EU Commission has also developed a criterion for identifying instances of food fraud that accounts for features such as identifiable violations of EU rules (as set out in Article 1(2) of Regulation (EU) 2017/625), deception, economic gain and intention. Directive 2001/110/EC limits human intervention that could alter the composition of honey and thereby allows for the preservation of the natural character of honey. It prohibits the addition of any food ingredient to honey, including food additives, and any other addition other than honey. Similarly, that Directive prohibits the removal of any constituent particular to honey, including pollen, unless such removal is unavoidable in the removal of foreign matter. Those requirements are in line with the Codex Alimentarius standard for honey (2001). Νon-compliance with the above mentioned guidelines constitutes honey an adulterated product.

Types of honey fraud

  1. Indirect honey adulteration pre-harvest

Anything that suggests improper feeding of honey bees with sugar during honey production or addition of sugars to honey falls into this category (Fig. 2). The sweeteners that can be used for this purpose are invert sugar syrups, high fructose corn syrups, syrups of natural origin such as maple, cane, sugar beet, molasses, etc. At present, these sweeteners are mainly feed syrups, produced by the hydrolysis of corn starch, cane sugar or sugar beet. Good beekeeping practice ensures that sweeteners used to feed the honey bees in the context of the stimulant feeding during the main nectar flow period should not be made to such an extent as to distort the honey. Nevertheless, the additional feeding in order to increase the yields in honey production is a serious form of fraud. Even untimely stimulant feeding may cause adulteration to the final product. This happens because sucrose syrup or isoglucose and other commercial feeds when administered to honey bees during the time they collect nectar and store it, are incorporated into honey and degrade its quality, distorting the final product. In general, the over-feeding of honey bees with syrup during the flowering period is a form of honey adulteration which is easily detected by the chemical characteristics of the product. In their attempt to increase the amount of honey produced, beekeepers sometimes feed the honey bees with sugar syrup in a ratio of 1:1. When this quantity exceeds the established standard limits, the quality characteristics of the honey are altered and if a relevant control is carried out – based on the quality criteria for a certain honey type, then the beekeeper will have to face serious penalties. Thus, feeding of this kind should be stopped at least one month before the forthcoming flowering period. Intense feeding during the summer months in order to fill the “gap of flowering”, may also affect the quality of the honey collected in the first harvest of autumn.

Figure 2. Supplementary feeding of honey bees with sugar solution during a research experiment.

2. Direct honey adulteration post-harvest

There are two cases in this category both aiming for higher commercial profits for honey producers. The first case concerns the possibility of blending the produced honey with various cheap sweeteners (like the ones already mentioned above), under the use of heating in order to achieve homogenization of the final product. Then, this blended mixture is resold as “genuine” honey. At a European level, almost a year ago, a supermarket chain withdrew pots of its own-brand honey amid concerns that it contains adulterated ingredients. In the second case, the honey production industry, uses glucose, caramel color or simply adds honey aroma to syrup through chemical treatments in order to produce a sweet substance resembling to honey. Another form of post-harvest adulteration is when honey is filtered or pasteurized in order to extend the shelf life. During this process, pollen is removed and along with it, all the benefits of its consumption.

3. Different botanical or geographical origin from that written on the label

Since honey bees visit various plant species, the honey produced is a mixture of different plant sources. Usually, honey is classified as being unifloral when at least 45% of pollen grains arise from a single species (with few exceptions). Consumer’s choice is linked to unique organoleptic and aromatic properties of honey that depend principally on the botanical and geographical origins of the product. Hence, the geographical categorization of honeys can raise its commercial value and contribute to the micro economy of the region. When certain types of honey (due to the varying preferences of consumers) are sold under higher prices in the market, honey producers may often provide the wrong botanical source of honey in order to mislead the consumer.

According to the European Directive 2001/110/EC, if honey originates from more than one member state or a country outside the European Union, this should be indicated in the product label as “blend of EU honey”, “blend of non-EU honey” (Fig. 3), or “blend of EU and non-EU honey” (Fig. 3). This provision is not valid in Codex (2001) leaving room for fraudulent listed information on the label. As for the so-called “local honey” it may not always be “local honey”, but cheap or low-quality honey imported from other countries, and then packaged and distributed locally (Fig. 4). Generally, legal standards and specifications for food, including the quality of honey, as well as tests for controlling honey adulteration vary widely between countries and continents.

Figure 3. Honeys with the indications “Blend of Non EU honeys” and “Blend of EU and Non EU honeys” on their labels.

Figure 4. The indication on this label is “Non-blended EU honey”. This closely resembles the indications that should be provided according to the guidelines of the European Directive 2001/110/EC, however, it does not clearly indicate the European country of origin.

4. Misbranding

Honey that contains misleading information on the label. In 2011, a multinational investigation on honey market fraud, uncovered the largest food industry fraud – Fifteen people across multiple countries were indicted for illegally diverting more than $80 million worth of honey from China to the United States. The practice of re-labelling the product with the intent to hide the country of origin is a considerable problem in the case of honey imported into the US, and is referred to as “honey laundering“. Another example is a honey that may deceitfully be labelled as “organic” notwithstanding the presence of antibiotics, pesticide, heavy metals or pesticide residues in the final product. Given the widespread use of chemical products in crops, it is difficult to guarantee that the honey produced by honey bees is “pure” (Fig. 5). When choosing honey in a store, it is almost impossible to distinguish pure from adulterated honey by simply looking at the contents in the jar or from the label. Unfortunately, a label with the indication “pure honey” on it, does not guarantee the content. Names such as “fresh” or “raw” honey may indicate that the honey in question is freshly harvested and has not been heat treated. Also, many honey production companies add high fructose corn syrup to their honey, which is made from genetically modified corn, and this may never be recorded on the label of the final product. According to the Irish Department of Agriculture, Food and the Marine, honey offered for sale to the consumer must comply with the European Communities (Marketing of Honey) Regulations 2003 (SI No. 367 of 2003). These regulations aim to ensure the honey is of acceptable quality and accurately labelled, especially in terms of origin.

Figure 5. Honeys with the indication “pure” on their labels.

General malpractices reducing honey quality

In addition to the various counterfeits that honey can suffer, there are other manipulations that beekeepers must pay special attention to, in order to avoid degrading the quality of the product produced; for example, the unorthodox use of chemical interventions in the hive and in the warehouse for the treatment of honey bee pathogens and diseases (e.g. to protect against varroa mites and nosemiasis). All the chemical treatments used in the hive encumber both honey and other honey bee products with residues that degrade the quality of the final product. The season and frequency of application, its type, the presence of open honey cells in the hive, and the rate of nectar secretion significantly affect the presence and concentration of chemical residues in honey. The EU has established limits for the maximum quantities of residues in EU honey and these limits should not be exceeded. However, many honeys sold in supermarkets are imported from countries outside the EU (e.g. China and India), and it is common for such products to be withdrawn because they contain banned and even carcinogenic antibiotics.

Harvest of unripe honey

Normally the water content of honey harvested in countries with mild climates is less than 18%. However, in some countries the collected honey has more than 20% humidity due to climatic or collecting conditions. Directive 2001/110/EC stipulates that honey bees dehydrate and store honey, leaving it in the honeycomb to mature after having sealed the cells. When the beekeeper harvests before the honey bees have time to “store, dehydrate and let it mature”, the water content can be as high as 25%. Asian beekeepers frequently harvest unripe honey with high water content, reducing the work of non-forager honey bees, who become foragers at an earlier age, thus, increasing the harvesting capacity of the colony and the producer’s yields. This honey is easily fermented before it is even transported to the place of artificial evaporation (honey factory), a practice that is not in accordance with the directions of Codex Alimentarius (2001). Moreover, the resulting product does not have the desired characteristics of an authentic honey.

Overheating of the product

Nowadays most commercial honeys are produced by centrifugation at 25-32˚C, similarly to the temperatures in the honeycomb cells. The use of heating for sterilization and liquefaction can adversely affect the quality of honey, such as the evaporation of volatile compounds and the reduction of enzyme activity. Alteration of the quality characteristics of honey can be performed by submitting it post-harvest to high temperatures, as well as during transport for international trade. When a producer wishes to mix his/her honey with another honey type in order to obtain more desirable characteristics for the consumer and thus facilitate its promotion on the market, he/she may use heating to facilitate the blending process, risking to alter the quality characteristics of the final honey blend.

Generally, it is difficult to be certain of the authenticity of honey without evaluating the samples in a scientific laboratory by performing specialized analyses with scientific methods such as magnetic resonance, Raman spectroscopy, DNA-based, carbon isotopes, electronic nose or electronic tongue etc. Nevertheless, if you try one of the methods discussed above or have a reason to suspect that the honey you bought is adulterated, I suggest staying away from that honey. Adulteration with cheaper sugars reduces the natural high quality of honey and constitutes this product not safe for consumption. According to a recent review study, six sugar based honey adulterants (cane sugar, corn syrup, palm sugar, invert sugar, rice syrup, and inulin syrup) were found to have a negative impact human health. Specifically, they impair the proper function of many body organs (liver, kidney, heart and brain), by increasing human’s blood sugar levels, causing diabetes, abdominal weight gain and obesity, raising blood pressure and lipid levels, and leading to arterial stenosis. However, the exact adverse effects of adulterated honey consumption on human health, are not fully established yet, due to the absence of systematic and scientific studies and lack of public awareness.

Two myths and two truths about honey

Two myths

“My honey granulates, I am pretty sure it is authentic good quality honey”.

In many cases a honey granulates, and from a liquid form it becomes a solid and a bit crunchy sweet mass.  Honey is a super-saturated solution of sugars, so it is only a matter of time before it will become granulated. In addition, some honeys from nectar of certain flowers are particularly prone to granulation (e.g. oilseed rape, clover, orange etc.). Buying honey in the honeycomb is (perhaps) a way to be more certain of the quality of the product as consumers can be sure that the honey has not been adulterated with sugar solution post-harvest (Fig. 6). However, this does not eliminate the possibility of an indirect pre-harvest honey fraud. Ultimately, these practices have an impact on the viscosity of honey produced, which resembles the viscosity of syrup – but this is not the rule.

Figure 6. Acacia honey sold along with the honey comb.

I bought this expensive honey. It must be of good quality“.

Prices are not always a good indication of the quality of honey. In cases of honey fraud, which have occurred in Chinese honey exports in the past, traders had combined different types of cheap and low-quality honey with expensive honey in order to increase the yield. On the other hand, the emergence of large quantities of adulterated honey, is driving prices down through the abundance of cheap, so-called “honeys”. A study conducted by the Canadian Government in 2019 found almost a quarter of commercial honey brands had been adulterated. Illicit products are eroding market prices and consumer trust, while causing significant damage to the beekeeping industry.

Two truths

Honey with darker color shade is richer in nutrients”.

Honey color depends on the flowering vegetation of the area where honey bees forage for nectar (Fig. 7). The color of honey can also be affected by the management practices of the beekeeper (e.g. how frequently the wax is changed), or by contact with metals and exposure to high temperatures and light. Thus, the color of honey may not be a good indication of its quality. However, darker honeys usually have a stronger flavor and are often richer in antioxidant agents than lighter honeys.

Figure 7. Various honey types and their respective color palette (Image modified from http://tzoumerkabees.blogspot.com/2011/06/blog-post.html).

“Honey does not really have an expiration date“.

Due to the current legislation, companies are obliged to assign an expiration date to the final product. But the truth is that unprocessed honey can be stored for long periods of time. So, once honey becomes granulated, it can be restored it to its previous state using the bain-marie heating method.

To conclude, it is up to you and your personal taste to choose the type of honey you want to consume. However, my advice is to always pay attention to all the information provided on the label (especially when you buy honey from the supermarket or if it is imported honey). I personally prefer consuming honey produced and packed in my local area, from the beekeeper of my town or from the official beekeeping organization in my country of residence.

Speaking about Irish honey, a recent study has shown that Irish heather honey had similar physiochemical characteristics to Manuka honey. So, why import 4,086 tons of honey from the other side of the world? Be a smart consumer, now you know!

About the author:

Since I was a young child, I grew up close to my grandfather who was a beekeeper himself. Close to him, I inherited his passion and respect for the honey bee community and witnessed the amazing natural process of honey making. Later on, during my undergraduate studies (School of Agriculture, Forestry and Natural Environment), I pursued doing my thesis on a honey bee related subject. It was when I learned about the different ways of honey adulteration and came across food fraud issues for the first time. Ever since, I became very sensitive in terms of what ends up in our table and how we, the consumers, can be more aware of our food choices.

Nowadays, I am also very sensitive in terms of what ends up in bees’ food, and I am still trying to figure that out with my study on ‘Characterizing pesticide residues in floral resources for bees’.

Elena Zioga is a 3rd year PhD student at Trinity College Dublin, working on the PROTECTS project, under the supervision of Jane Stout and Blanaid White.