Environmental factors affect melezitose production in honeydew from aphids and scale insects of the order Hemiptera

Honeydew honey belongs to the main honey sorts produced in European countries. Phloem sap feeding insects of the order Hemiptera excrete honeydew and honey bees process it into honey. In the case of high osmolality in the phloem sap, hemipteran species counteract osmotic pressure by producing oligosaccharides such as melezitose. Melezitose is a poorly digestible food source for bees, which can lead to honeydew flow disease. Moreover, melezitose-rich honey crystallises quickly and leads to economic losses for beekeepers. To understand the effects of diverse environmental factors on melezitose production, we analysed melezitose proportions with high performance anion-exchange chromatography of 620 honeydew samples collected between 2016 and 2019 considering botanical, zoological, geographical, and meteorological factors. We conducted a two-part logit-model considering all possible variables that could affect melezitose production simultaneously. Higher air temperatures and lower relative humidity levels increased melezitose production. Scale insect species and aphid species on Abies alba produced significantly less honeydew containing melezitose than aphid species on Picea abies. Honeydew with melezitose content was collected more often in natural areas with limited water reservoir capacities. All results lead to the conclusion that in the case the host trees have less access to water and an increasing osmolality of the phloem sap, the melezitose production by hemipteran species is indirectly enhanced. Our results may serve as an indicator of melezitose production and contribute to warning systems for beekeepers that help prevent harmful nutrition for bees or crystallised honey by timely removal of bee colonies from regions at risk.