Melezitose: origins, risks and practical management at the apiary

0. Introduction: when does melezitose become a problem?

Objective: to raise the central question of the article and show that melezitose is not in itself a defect, but becomes problematic in two specific contexts: the harvest and overwintering.

At the apiary, melezitose is often associated with the idea of "cement honey". This association is not wrong, but it is incomplete. Melezitose is not in itself a defect of honey: it is a natural constituent of certain honeydew flows, and its practical importance depends entirely on the context. It becomes critical above all in two clearly distinct situations: when the honey crystallises in the combs before extraction, and when melezitose-rich stores remain in the brood box for overwintering (Imdorf et al., 1985).

For the harvest, the decisive point is therefore not the mere presence of melezitose, but its effect on the speed and intensity of crystallisation in the combs. As long as the flow is identified in time and extraction takes place before the frames become blocked, melezitose does not automatically mean a loss of harvest. The problem arises when crystallisation progresses to the point of making the honey difficult, then impossible, to extract by centrifugation (Imdorf et al., 1985).

The second situation concerns overwintering. Swiss work carried out after the 1984 flow showed that colonies overwintering on honey heavily loaded with melezitose could display high losses, signs of dysentery and a difficult spring build-up (Imdorf et al., 1985). More recent work helps to understand this risk: in bees fed on diets rich in melezitose, researchers observed increased food intake, a heavier digestive tract, intestinal symptoms and reduced survival, particularly under conditions in which waste elimination is limited, as in winter (Seeburger et al., 2020).

Two misreadings should therefore be avoided. The first would be to reduce the problem to a mere question of forest honey. The second would be to underestimate a real risk to the colony.

This article therefore starts from a simple question: at what point does melezitose become a concrete beekeeping problem? To answer it, one must first understand what melezitose is, where it comes from in the forest honeydew flow, and then clearly distinguish its possible consequences for the harvest from those for overwintering. It is this distinction that makes it possible to reason correctly at the apiary, without unnecessarily dramatising but also without underestimating the real risks (Imdorf et al., 1985; Seeburger et al., 2020; Seeburger et al., 2022).

1. What is melezitose?

Melezitose is a solid that melts at around 153 °C and is soluble in hot water. Its molar mass is 504.44 g/mol and its chemical formula is C18H32O16.

Objective: to define melezitose simply and show that it is a natural sugar from certain honeydew flows, produced during the transformation of the sap by the insect and then worked by the bees into honey.

Melezitose is a trisaccharide, that is, a sugar made up of three units. It occurs above all in certain honeydew flows, and then in the honeydew honeys that bees produce from them. It is therefore neither a contaminant nor a defect arising after harvest, but a natural constituent of certain forest honeydew flow situations (Seeburger et al., 2020; Seeburger et al., 2022).

To place it properly, one must start from the phloem sap. Honeydew-producing insects, in particular certain aphids and scale insects, feed on this sap, which is rich in sucrose. As it passes through their digestive tract, some of this sucrose is transformed into other sugars, including melezitose. The excreted honeydew is then collected by the bees, which work it into honey (Seeburger et al., 2022; Shaaban et al., 2020).

An important point is that melezitose should not be understood simply as a "sugar from the tree". Comparisons between phloem exudates and honeydew show that the exudates of the trees analysed do not contain trisaccharides, whereas honeydew does, notably melezitose and erlose. In other words, melezitose appears mainly during the transformation of the sap by the honeydew-producing insect (Shaaban et al., 2020).

For the beekeeper, melezitose can therefore be defined simply: it is a natural sugar from certain honeydew flows, produced in the interaction between the tree, the honeydew-producing insect and, subsequently, the bee. Its presence does not automatically mean that a honey is problematic, but it becomes important as soon as it influences crystallisation in the combs or the suitability of stores as winter feed (Imdorf et al., 1985; Shaaban et al., 2020).

2. Where does melezitose in the forest honeydew flow come from?

Honeydew-producing aphids on a branch of Picea abies (Cinara pruinosa or Cinara stroyani).

Objective: to explain that the risk of melezitose depends above all on the honeydew-producing insects and on the conditions of the year, and not merely on the fact that it is a forest honeydew flow.

Melezitose does not occur uniformly in every honeydew flow. It depends first on the honeydew-producing insects present on the trees and then on the conditions under which they feed. Two forest stands that look comparable to the beekeeper will not necessarily give the same melezitose risk, even if both fall under a so-called "forest" flow (Shaaban et al., 2020; Seeburger et al., 2022).

Studies comparing different honeydew producers on Abies alba and Picea abies show that the sugar composition of honeydew depends more on the hemipteran species than on the host tree itself. In the study by Shaaban et al. (2020), melezitose contents varied widely between species: some species associated with spruce, such as Cinara piceae and Cinara pilicornis, showed markedly higher proportions than other honeydew producers, while other species, including on fir, showed profiles richer in erlose than in melezitose. At the apiary, this means that simple shortcuts such as "fir = this" or "spruce = that" should be avoided: it is primarily the honeydew producers actually present that shape the profile of the forthcoming honey (Shaaban et al., 2020).

Weather conditions also play an important role. In the study by Seeburger et al. (2022), carried out on 620 honeydew samples in southern Germany, higher temperatures and lower relative humidity were associated with increased melezitose production. The authors interpret this result in relation to the water supply of the host trees: when the tree has less water available, the sap becomes more concentrated, which seems to promote an increased conversion of sucrose into oligosaccharides such as melezitose by the honeydew-producing insects. Melezitose thus appears more readily in contexts of warmth, relative dryness and limited water availability (Seeburger et al., 2022).

In the Central European system studied, aphid species associated with spruce proved particularly important for melezitose-rich honeydew. This does not mean that spruce alone produces melezitose, nor that every spruce flow leads to "cement honey". Rather, it means that certain combinations of spruce, honeydew-producing species and warm, dry conditions appear more favourable to high melezitose levels than others (Shaaban et al., 2020; Seeburger et al., 2022).

The practical consequence for the beekeeper is important: a risk flow cannot be reduced to a tree species or to the generic label "forest honey". It results from a combination of the type of honeydew produced, the insects present, the year's weather context, and the speed with which the situation evolves in the combs. That is why some years pass without any particular difficulty, while others tip in a few days into problematic crystallisation (Imdorf et al., 1985; Seeburger et al., 2022).

3. When does melezitose become a problem for the harvest?

Objective: to show at what point melezitose becomes a concrete problem for the harvest, while distinguishing this mechanism from other rapid crystallisations, notably in certain glucose-rich spring flows.

For the harvest, the question is not whether a honey contains melezitose, but to what extent this melezitose causes the honey to crystallise in the combs. As long as the honey remains extractable, its presence does not in itself constitute a major production problem. The practical tipping point occurs when crystallisation becomes advanced enough to slow down strongly, and then prevent, extraction by centrifugation (Imdorf et al., 1985).

In the classical Swiss literature, the term "Zementhonig" (cement honey) designates precisely this situation: a honeydew honey crystallised in the combs and often impossible to extract normally. The authors indicate that above about 10 to 12 % melezitose, honey crystallises in the cells, and that the higher the content, the greater the degree of crystallisation (Imdorf et al., 1985). This indication is useful as a practical reference point at the apiary: it does not mean that a slightly melezitose-rich honey is necessarily lost, but that from this level onwards, the risk of comb blockage begins to rise, and becomes particularly high when the content approaches or exceeds 20 %, a level at which the combs can quickly become blocked.

However, two crystallisation mechanisms must be distinguished. In some honeydew honeys, rapid crystallisation is mainly due to a high melezitose content. In many blossom honeys, by contrast, it depends rather on high glucose and a low fructose-to-glucose ratio. The case of rape honey is classic, and dandelion can go in the same direction. In other words, a honey can crystallise quickly without being rich in melezitose. This distinction is important at the apiary, especially for certain spring flows: in such cases, the risk concerns mainly handling and the timing of extraction, not the wintering health of the bees.

More recent studies point in the same direction. Seeburger et al. (2022) recall that honeys containing at least 20 % melezitose crystallise quickly and can clog the combs to the point of becoming non-extractable. In this logic, the beekeeping problem is therefore not merely the presence of this sugar, but the combination of its proportion, the speed of crystallisation and the moment at which the beekeeper intervenes (Seeburger et al., 2022).

This has an important practical consequence: a melezitose-rich honeydew honey can still remain usable for the harvest if it is identified early enough and extracted before the frames become blocked. If one waits too long, the situation can deteriorate rapidly and turn an economically attractive flow into a harvest that is very difficult, or even impossible, to extract (Imdorf et al., 1985; Seeburger et al., 2022).

Two levels must therefore be distinguished. At the first level, melezitose is simply part of the sugar profile of certain honeydew honeys. At the second, it becomes a management problem when crystallisation progresses in the supers or in the combs of the brood box. It is this second level that concerns the beekeeper: not to condemn on principle a melezitose-rich honeydew honey, but to know from what point the harvest window closes (Imdorf et al., 1985).

4. Why does melezitose become more delicate for overwintering than for the harvest?

Objective: to explain why a melezitose-rich honey is above all an overwintering problem when it remains as the main stores in the brood box, whereas the harvest risk follows a different logic.

The main difficulty with melezitose is not the same at harvest and in winter. At harvest, the problem is mainly mechanical: the honey crystallises in the combs and becomes difficult to extract. In overwintering, the question is different: whether these stores remain usable and tolerable for the bees during a period when cleansing flights are rare or impossible (Imdorf et al., 1985; Seeburger et al., 2020).

The Swiss field observations describe this situation clearly. At the Wohlei experimental apiary, colonies overwintered on melezitose-rich stores without supplementary syrup feeding suffered high winter losses, with signs of dysentery and a very weakened spring build-up. In the survey carried out subsequently among beekeepers, losses increased sharply with the melezitose content of the winter feed: they were low when the reserve honey remained below 10 %, but clearly higher above this level, and higher still above 20 % (Imdorf et al., 1985).

Recent experimental work helps to understand why. In cage trials, bees fed on diets rich in melezitose showed higher consumption, an increased ratio of digestive tract weight to body weight, marked intestinal symptoms and reduced survival. The authors link these effects to difficult digestion of melezitose and to its accumulation in the hindgut, which becomes particularly unfavourable when the bees cannot regularly eliminate their waste by flying (Seeburger et al., 2020).

Field data point in the same direction without conflating everything. In the Austrian COLOSS survey of 33 651 colonies, honeydew in general was not associated with a rise in winter losses, whereas beekeepers reporting a melezitose flow did report higher losses. This nuance is important: it is not forest honey as such that seems to pose a problem, but certain melezitose-rich honeydew situations, especially when they interfere with overwintering (Oberreiter & Brodschneider, 2020).

In the first case, the issue is mainly honey recovery. In the second, it is the survival and the quality of the colony's spring build-up that are at stake (Imdorf et al., 1985; Seeburger et al., 2020).

5. What to do concretely at the apiary?

Objective: to translate the findings into concrete decisions at the apiary: monitor the flow, extract in time, reduce risky stores in the brood box, and clearly distinguish honey recovery from the normal building-up of winter stores.

At the apiary, the first rule is to clearly separate the question of the harvest from that of overwintering. If a melezitose-rich honeydew flow is still under way, the main issue is to observe the evolution of the combs and not to miss the extraction window. If, on the other hand, already crystallised stores are in the brood box at the end of the season, the issue becomes the safety of overwintering. In both cases, waiting too long worsens the situation, either because the supers become blocked or because the brood box remains loaded with stores that are poorly suited to winter (Imdorf et al., 1985; Seeburger et al., 2022).

When harvest is still possible, reasoning must therefore be in terms of responsiveness. A melezitose-rich flow is not necessarily lost, but it can tip quickly into troublesome crystallisation in the combs. In this context, the most prudent approach is to monitor closely the speed of filling and the appearance of the frames, then to extract before the honey becomes frankly non-centrifugable. It is the progression of crystallisation in the combs, and not the mere presence of melezitose, that turns a good honeydew flow into a technical problem (Imdorf et al., 1985; Seeburger et al., 2022).

If melezitose-rich honeydew honey has already been stored in the combs of the brood box, the priority is to reduce as far as possible the share of these stores in the future winter nest. The Swiss work by Imdorf et al. (1985) concludes that this honey should, as far as possible, be removed before autumn feeding. The authors also indicate that it may be useful to insert empty combs, or even to replace some full frames, in order to increase the likelihood that the syrup will be stored where the bees will actually overwinter. In their survey, losses were markedly lower when colonies had received more than 8 litres of 1:1 syrup, from which they derived the practical reference of at least about 10 litres of 1:1 syrup per colony to reduce the melezitose-related risk. This point, however, should not be confused with the overall level of stores required for overwintering, which has to be planned separately according to colony strength, hive format and local management references. In the usual management benchmarks, the complete build-up of winter stores is on a different order of magnitude; in the ApiService schemes, the target is rather around 16 to 20 kg of stores.

When the honey is already too crystallised to be extracted normally, the solution regarded as most promising in the Swiss work by Imdorf et al. (1985) is to let the bees rework the combs. The "cement honey" combs are then scratched open, and returned in such a way that the bees can remobilise part of the content and relocate it elsewhere. The authors describe this method as the best way to recover part of the honey, while also showing its limits: the operation can be slow, the aggressiveness of the colonies can increase, and the yield remains variable. They also showed that a significant proportion of the crystals removed during this process consisted almost exclusively of melezitose (Imdorf et al., 1985). Other procedures also make it possible to recover part of the honey, but their effects are not the same. Dissolution in water exposes the honey above all to a high risk of fermentation and to a deterioration in quality linked to the increased water content. Recovery by strong heating, in particular in a cappings melter, clearly alters enzymatic activity and may change taste, water content and product compliance. In the Swiss framework presented by Agroscope, honey obtained in the cappings melter no longer qualifies as "natural honey from good beekeeping practice" and must be used or sold as baker's honey (Kast et al., 2025).

6. Key points to remember

Objective: to summarise in a few simple reference points what a beginning or intermediate beekeeper should remember in order to identify a risky flow and avoid the costliest mistakes, both at harvest and at overwintering.

• Melezitose is not in itself a defect. It is a natural sugar from certain honeydew flows. The problem starts above all when the honey crystallises quickly in the combs, or when these stores remain in the brood box for winter.
• Not all forest honeys carry the same risk. The outcome depends on the honeydew-producing insect, on the host tree and on the conditions of the year, especially in hot and dry weather.
• For the harvest, the key point is timing. A melezitose-rich honey can still be harvestable if one intervenes early enough. If one waits too long, the frames can quickly become blocked.
• For overwintering, these stores should not be left in the brood box. The real danger is not forest honey in general, but melezitose-rich honeydew stores left in the wrong place at the wrong time.
• At the apiary, the approach remains simple: monitor risky flows, extract without delay if crystallisation advances, reduce the share of melezitose-loaded frames in the winter nest, and then build up winter stores normally according to the usual management reference points.
• In short: the right question is not "is it forest honey?", but "is this honey now at risk of blocking the harvest or complicating overwintering?"

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See also:

• Crystallisation of honey
• The honey harvest
• Succeeding with overwintering
• Which syrup to choose for winter feeding
• Practical Guide: 4.2 Feeding
• August at the apiary

 

Bibliography

Imdorf, A., Bogdanov, S., & Kilchenmann, V. (1985). «Zementhonig» im Honig- und Brutraum – was dann? 1. Teil: Wie überwintern Bienenvölker auf Zementhonig? Schweiz. Bienenztg., 108(10), 534–544.

Imdorf, A., Bogdanov, S., Kilchenmann, V., & Wille, H. (1985). «Zementhonig» im Honig- und Brutraum – was dann? 2. Teil: Wirkt «Zementhonig» als Winterfutter toxisch? Schweiz. Bienenztg., 108(11), 581–590.

Oberreiter, H., & Brodschneider, R. (2020). Austrian COLOSS Survey of Honey Bee Colony Winter Losses 2018/19. Diversity, 12(3), 99. https://doi.org/10.3390/d12030099

Seeburger, V. C., D'Alvise, P., Shaaban, B., Schweikert, K., Lohaus, G., Schroeder, A., & Hasselmann, M. (2020). The trisaccharide melezitose impacts honey bees and their intestinal microbiota. PLOS ONE, 15(4), e0230871. https://doi.org/10.1371/journal.pone.0230871

Seeburger, V. C., Shaaban, B., Schweikert, K., Lohaus, G., Schroeder, A., & Hasselmann, M. (2022). Environmental factors affect melezitose production in honeydew from aphids and scale insects. Journal of Apicultural Research, 61(1), 127–137. https://doi.org/10.1080/00218839.2021.1957350

Shaaban, B., Seeburger, V., Schroeder, A., & Lohaus, G. (2020). Sugar, amino acid and inorganic ion profiling of the honeydew from different hemipteran species feeding on Abies alba and Picea abies. PLOS ONE, 15(1), e0228171. https://doi.org/10.1371/journal.pone.0228171

Kast, C., Droz, B., Rietveld, L., & Fracheboud, M. (2025). Melezitose honey: implications for the beekeeper; influence of heat on honey quality. Continuing education course for bee health advisors and farm inspectors, Swiss Bee Research Centre, Agroscope, 1 March 2025.