Where honeydew comes from: the trees, the insects and the honey

Three parties, not two

Phloem sap — the stream that carries a tree's sugars from its leaves to the rest of the plant — is rich in sugar and poor in nitrogen. An insect that lives on it has to pass a great deal of sap to collect enough protein, and it gets rid of the surplus sugar and water as droplets of honeydew. Aphids, soft and giant scale insects, planthoppers and psyllids all do this. Bees collect the droplets from needles, leaves and bark, add their enzymes, evaporate the water and store the result as honey.

So a honeydew honey has three parties where a floral honey has two. The tree supplies the raw material, the insect transforms it — adding sugars of its own making and changing the balance of those it passes — and the bee finishes it. No flower is involved and no pollination happens, which makes honeydew the clearest case of honey production and pollination being entirely separate things.

The documented chains

The table below lists the tree–insect links HoneyHQ has found documented in published surveys, analyses or reference descriptions of honey types. It is deliberately explicit about how each link is known, because honeydew writing routinely merges four different things — the tree the sap came from, the insect that processed it, the region the honey was made in, and a laboratory measurement — into a single confident sentence.

The insect matters more than the tree

The clearest evidence comes from a study that collected honeydew straight from insect colonies — two aphids on silver fir, and two aphids and two scale insects on Norway spruce, at least fifteen colonies each, in Baden-Württemberg in 2016 and 2017. When the composition of every sample was compared, the insect species explained 47.8 per cent of the variation and the tree species 13.7 per cent. Two insects on the same spruce produced honeydew as different as honeydews from two different trees.

Melezitose is the sugar that makes the difference to a beekeeper. It is a three-part sugar made in the insect rather than the tree, and it is poorly soluble: honeydew rich in it can crystallise in the comb before it can be extracted, the 'cement honey' of central European forest beekeeping. The black spruce aphid, Cinara piceae, produced honeydew that was on average 48 per cent melezitose. The two fir aphids produced almost none. That one fact explains more about a forest honey's behaviour in the jar than the name of the tree on its label.

Why honeydew honey tests differently

The insect's contribution shows up in every standard measurement. In the European reference data, honeydew honeys carry less fructose and glucose combined — under 60 grams in every hundred against about 70 for blossom honeys — because the insect-made sugars take up the difference. They turn polarised light to the right where every blossom honey turns it to the left. They conduct electricity more strongly, because honeydew has passed through both a tree and an insect and carries more minerals. And under the microscope they show honeydew elements — fungal hyphae, spores and single-celled algae that grow on sugary leaf surfaces — alongside pollen from wind-pollinated trees that offer bees no nectar at all.

One honeydew honey is chemically distinct enough to be described on its own: the honey made from the excretion of Metcalfa pruinosa, a North American planthopper that reached Europe at the end of the 1970s. It has the highest conductivity of any type in the European descriptions, an acidity that can exceed the general legal limit, and a high dextrin content — and because the planthopper feeds on hundreds of plants, it can be produced in landscapes with no forest at all.

Why a honeydew flow cannot be planned

A floral flow follows a flowering calendar. A honeydew flow follows an insect population, and insect populations boom and crash for reasons invisible from the ground — weather, predators, parasitoids, the condition of the tree. In the Turkish forest survey, the cedar aphid was present in small numbers with very little honeydew in 2016 and 2017 and then built a large population in the autumn of 2018. Beekeepers who depend on honeydew move colonies into the forest at short notice when a flow appears, and some years there is none.

The giant pine scale behind Greek and Turkish pine honey is the partial exception, because it is a single, well-studied insect with one generation a year: it overwinters as a young nymph and produces its heaviest honeydew in March and April, before its final moult. Greek entomologists report pine honey as about 60 per cent of Greece's annual honey production, which makes the country's honey output unusually dependent on one scale insect. The insect has also been moved deliberately into new pine stands to create honey flows — a practice argued over on forest-health grounds.