Per Kryger

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Verified

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• Dr. rer. nat. cand. scient.
• Senior Researcher at Aarhus University

Pollen is a source of protein, lipids, vitamins and minerals for bees and other flower-visiting insects. The composition of macro- and micronutrients of pollen vary among different plant species. Honey bees are long-distance foragers, collecting nectar and pollen from plants within several kilometers of their hive. Availability of pollen within the...

Pollen and nectar consumed by honey bees contain plant secondary metabolites (PSMs) with vital roles in plant–insect interactions. While PSMs can be toxic to bees, they can also be health-promoting, e.g. by improving pesticide and pathogen tolerances. As xenobiotics, PSMs undergo post-ingestion chemical modifications that can affect their bioactivi...

Here, we cover a wide range of methods currently in use and recommended in modern queen rearing, selection, and breeding. The recommendations are meant to serve as standards for scientific and practical beekeeping purposes. The basic conditions and different management techniques for queen rearing are described, including recommendations for suitab...

Pollen is a source of protein, fats, vitamins and minerals for honey bees, and pollen nutri- tion is important for bee health and winter survival. In this study, we investigated the pollen supply of honey bees in Danish landscapes with a view to elucidate the significance of the seasonal development and land use in the surrounding landscape. The re...

Honey bee subspecies originate from specific geographic areas in Africa, Europe and the Middle East, and beekeepers interested in specific phenotypes have imported genetic material to regions outside of their original range for use either in pure lines or controlled crosses. Moreover, imported drones are present in the environment and mate naturall...

In order to investigate the geographical distribution of morphological and mitochondrial variation of the Western honey bee in West and Central Africa, 175 colonies, sampled from 44 localities (or a subset therefrom), were subjected to geometric morphometric (GM), traditional morphometric (TM) and mitochondrial DNA analyses. The shape of the forewi...

Background: Whole-genome sequencing has become routine for population genetic studies. Sequencing of individuals provides maximal data but is rather expensive and fewer samples can be studied. In contrast, sequencing a pool of samples (pool-seq) can provide sufficient data, while presenting less of an economic challenge. Few studies have compared...

Honey bee subspecies originate from specific geographic areas in Africa, Europe and the Middle East. The interest of beekeepers in specific phenotypes has led them to import subspecies to regions outside of their original range. The resulting admixture complicates population genetics analyses and populations stratification can be a major problem fo...

Agricultural and apicultural practices expose honeybees to a range of pesticides that have the potential to negatively affect their physiology, neurobiology, and behavior. Accumulating evidence suggests that these effects extend to the honeybee gut microbiome, which serves important functions for honeybee health. Here we test the potential effects...

Plant reproduction in red clover requires cross-fertilization via insect pollination. However, the influences of visitation rate and timing on maximizing ovule utilization are yet to be determined. We aimed to study the influences of visitation rate, flowering stage, and self-incompatibility on reproductive success. We applied hand and honey bee po...

As part of the MUST-B project, a research project on field data collection for honey bee colony model evaluation was carried out in 2018-2020. In a preparatory phase (2018), methods for monitoring of honey bee colonies were tested, field operators trained, and experimental colonies established. The main field experiment was conducted in 2019-2020,...

The losses of honey bee colonies and declines of other insect pollinators have been associated with negative effects of pesticides. Honey bees as well as other pollinators are nectar and pollen foragers and thus are exposed to an extensive range of phytochemicals. Understanding the synergistic, additive, and antagonistic effects of plant secondary...

In red clover seed production, low seed yield is limiting the commercial exploitation of tetraploid red clover. To explore if pollination is the limiting factor for the seed yield in tetraploid red clover, we investigated pollinator behaviour and plant reproductive success in diploid (2x) cultivar ‘Rajah' and tetraploid (4x) cultivar ‘Amos' using h...

A recurrent concern in nature conservation is the potential competition for forage plants between wild bees and managed honey bees. Specifically, that the highly sophisticated system of recruitment and large perennial colonies of honey bees quickly exhaust forage resources leading to the local extirpation of wild bees. However, different species of...

Red clover (Trifolium pratense L.) is an important forage legume grown in many of the temperate regions around the world. In order to evaluate possible causes for the low seed yield in particular in tetraploid red clover, we surveyed 71 studies of red clover seed production published from 1948 to 2019, reviewing seed yield components, pollination a...

Background With numerous endemic subspecies representing four of its five evolutionary lineages, Europe holds a large fraction of Apis mellifera genetic diversity. This diversity and the natural distribution range have been altered by anthropogenic factors. The conservation of this natural heritage relies on the availability of accurate tools for s...

The honey bee pollen/nectar diet is rich in bioactive phytochemicals and recent studies have demonstrated the potential of phytochemicals to influence honey bee disease resistance. To unravel the role of dietary phytochemicals in honey bee health it is essential to understand phytochemical uptake, bioavailability, and metabolism but presently limit...

Honey bees are important pollinators and are subject to numerous stressors, such as changing floral resources, parasites, and agrochemical exposure. Pesticide exposure has been linked to the decline in the global honey bee population. We have limited knowledge of the metabolic pathways and synergistic effects of xenobiotics in bees. Quercetin is on...

In the fight against the Varroa destructor mite, selective breeding of honey bee (Apis mellifera L.) populations that are resistant to the parasitic mite stands as a sustainable solution. Selection initiatives indicate that using the suppressed mite reproduction (SMR) trait as a selection criterion is a suitable tool to breed such resistant bee pop...

Honey bees regularly ingest quercetin, one of the most abundant phytochemicals in plants. Past research suggests that honey and pollen feeding upregulates the bees’ detoxification system and that dietary quercetin reduces the toxicity of imidacloprid and tau-fluvalinate. The aim of this study was to investigate the effect of dietary quercetin on th...

Nowadays the Western honey bee (Apis mellifera) is present worldwide, wherever beekeeping is possible, though its native habitat spreads out across Europe, Africa and parts of Western Asia. About 26 different subspecies evolved through time, each adapted by natural selection to cope with the local environmental conditions. During the past 2 centuri...

On the graph on the left 3000+ honey bees collected across Europe are differentiated into subspecies and local ecotypes using the 4000+ SNPs developed in SmartBees. In the top a cluster of samples consisting of O-lineage bees, to the right M-lineage bees, to the left C-lineage bees and central the A-lineage bees. Subspecies that appear in close pro...

This paper presents a portable computer vision system, that is able to monitor the infestation level of the Varroa destructor mite in a beehive by recording a video sequence of live honeybees Apis mellifera for 5–20 min. A video monitoring unit with multispectral illumination and camera was designed to be placed in front of the beehive, where bees...

Declining honey bee (Apis mellifera) populations are receiving increasing attention especially because honey bees are important pollinators of our food crops. The underlying cause of the decline is hypothesized to be multifactorial and honey bees face many stressors including pathogens, xenobiotics, and changes in floral resources. Multitudes of...

Relevance: Honey bees (Apis mellifera) are exposed to a range of agrochemicals when they pollinate our fields1,2. The neonicotinoid imidacloprid, the pyrethroid tau-fluvalinate and a triazole fungicide tebuconazole are common xenobiotics that induce stress in honey bees. Mao et al3 demonstrated that quercetin can up-regulate the detoxification syst...

The natural distribution of the honeybee (Apis mellifera L.) has been changed by humans in recent decades to such an extent that the formerly widest-spread European subspecies, Apis mellifera mellifera, is threatened by extinction through introgression from highly divergent commercial strains in large tracts of its range. Conservation efforts for A...

Deformed wing virus (DWV) is an important pathogen in a broad range of insects, including honey bees. Concordant with the spread of Varroa, DWV is present in the majority of honey bee colonies and can result in either low-level infections with asymptomatic bees that nonetheless exhibit increased colony loss under stress, or high-level infections wi...

DWV and SBV titers in different experiment. The virus titer for the three experiments are deposited in the supplementary file. (XLSX)

To evaluate the performance of the molecular methods used by national reference laboratories (NRLs) for the identification of Nosema species in bee samples, an inter-laboratory comparison (ILC) was organised in 2015. A total of 20 EU NRLs and 1 non-European NRL participated in this ILC. The specificity of the methods was tested on various Nosema sp...

Nosema ceranae is an intracellular microsporidian parasite that infects epithelial cells of the honey bee (Apis mellifera) midgut. Previous studies have shown that Nosema may alter cell renewal and apoptosis in honey bees. We found that the amount of apoptotic cells progressively declines from the anterior towards posterior regions of the midgut in...

Fig. 1. Neighbour-joining phylogenetic tree constructed using 523 nt from published sequences of the CBPV RNA polymerase coding sequence (deposited in GenBank database) and the sequence of CBPV isolate Sophia-2014-H20 (Accession number: KX779523) selected for the inter-laboratory comparison (arrow). The sequences are identified by the CBPV isolate...

Beauveria bassiana is an entomopathogenic fungus that grows both in vivo and in vitro. In vivo it can colonize live insect hosts, and tissue digestion occurs by secreted hydrolytic exoenzymes. It can also colonize dead insect tissue provided this is free from competing microorganisms. Depending on whether the host is alive or dead the expression (q...

The disease deformed wing virus in bees can be transmitted when the bees mate, leading to colony collapse. When a queen has sex with many different partners, it can increase her risk of infection with venereal disease. It can also lead to the collapse of her colony. This might read like ingredients for a juicy novel, but for bees it is reality. Sci...

Deformed wing virus is an important contributor to honey bee colony losses. Frequently queen failure is reported as a cause for colony loss. Here we examine whether sexual transmission during multiple matings of queens is a possible way of virus infection in queens. In an environment with high prevalence of deformed wing virus, queens (n = 30) were...

With the aim of contributing to the development of models forecasting the melliferous characteristics and the potential honey yield of oilseed rape, we analyzed data on the temporal pattern of number of oilseed rape flowers, nectar secretion, sugar concentration, and weight of bee hives in relation to meteorological parameters, across three seasons...

With the aim of contributing to the development of decision support tools for migratory beekeepers in their planning for hive movements to heathlands in time and space, models were developed from analyses of heather flowering, nectar secretion, sugar concentration, and weight of bee hives in relation to meteorological parameters across two seasons...

Host-pathogen coevolution leads to reciprocal adaptations, allowing pathogens to increase host exploitation or hosts to minimise costs of infection. As pathogen resistance is often associated with considerable costs, tolerance may be an evolutionary alternative. Here, we examined the effect of two closely related and highly host dependent intracell...

In honey bees, multiple mating of queens with often more than 20 drones, known as polyandry, is extreme. At the colony level, polyandry can provide fitness gains through better division of labor and disease resistance. For the honey bee queen polyandry may pose a risk, for instance through sexually transmitted diseases. Deformed wing virus (DWV) is...

We present a fully automatic online video system, which is able to detect the behaviour of honeybees at the beehive entrance. Our monitoring system focuses on observing the honeybees as naturally as possible (i.e. without disturbing the honeybees). It is based on the Raspberry Pi that is a low-cost embedded computer with very limited computational...

Honey bees (Apis mellifera) are important pollinators and their health is threatened worldwide by persistent exposure to a wide range of factors including pesticides, poor nutrition, and pathogens. Nosema ceranae is a ubiquitous microsporidian associated with high colony mortality. We used lab micro-colonies of honey bees and video analyses to trac...

Honey bee virus prevalence data are an essential prerequisite for managing epidemic events in a population. A survey study was carried out for seven viruses in colonies representing a healthy Danish honey bee population. In addition, colonies from apiaries with high level Varroa infestation or high level of winter mortality were also surveyed. Resu...

Apoptosis is not only pivotal for development, but also for pathogen defence in multicellular organisms. Although numerous intracellular pathogens are known to interfere with the host’s apoptotic machinery to overcome this defence, its importance for host-parasite coevolution has been neglected. We conducted three inoculation experiments to investi...

Since its establishment in 2008, the COLOSS (Prevention of honey bee COlony LOSSes) association has been successful in bringing together bee research scientists, bee health specialists and extension advisors to study the causes of global honey bee losses, and now has a substantial output of papers published in refereed scientific journals. The newl...

Over the last few decades, a gradual departure away from traditional agricultural practices has resulted in alterations to the composition of the countryside and landscapes across Europe. In the face of such changes, monitoring the development and productivity of honey bee colonies from different sites can give valuable insight on the influence of...

The honey bee Apis mellifera, of which there are currently 28 identified subspecies and numerous ecotypes, have been evolving and adapting to a wide range of environments for hundreds of thousands of years within their native range of Europe, Africa and Asia. Honey bees have been widely dispersed over the past several hundred years and are now also...

Beekeeping activities, especially queen trading, have shaped the distribution of honey bee (Apis mellifera) subspecies in Europe, and have resulted in extensive introductions of two eastern European C-lineage subspecies (A. m. ligustica and A. m. carnica) into the native range of the M-lineage A. m. mellifera subspecies in Western Europe. As a cons...

Beekeeping activities, especially queen trading, have shaped the distribution of honey bee (Apis mellifera) subspecies in Europe, and have resulted in extensive introductions of two eastern European C-lineage subspecies (A. m. ligustica and A. m. carnica) into the native range of the M-lineage A. m. mellifera subspecies in Western Europe. As a cons...

Hygienic behaviour in the honey bee, Apis mellifera, is the uncapping and removal of dead, diseased or infected brood from sealed cells by worker bees. We determined the effect of hygienic behaviour on varroa population growth and incidence of deformed wing virus (DWV), which can be transmitted by varroa. We treated 42 broodless honey bee colonies...

Honey bee colony losses have risen seriously in the past decade, especially in the USA. In Europe, average loss rates appear less dramatic and high losses occur less frequently; still, high losses may happen on a regional scale. Scientists and beekeepers are struggling to find answers to this problem. Queen loss and infertility is frequently consid...

cecilia.costa@entecra.it The aim of this study was to investigate the effects of genotype-environment interactions on the survival, performance and disease susceptibility of honey bee colonies headed by queens originating from several areas in Europe. We included 16 different genotypes from different backgrounds (some from breeding programs with s...

The term “quality” in relation to queens and drones refers to certain quantitative physical and / or behavioural characters. It is generally believed that a high quality queen should have the following physical characteristics: high live weight; high number of ovarioles; large size of spermatheca; high number of spermatozoa in spermatheca; and be f...

The genetic variability of honey bees (Apis mellifera L.) from south eastern Europe was investigated using microsatellite analyses of 107 samples from Albania, the Republic of Macedonia, Greece and Bulgaria together with 42 reference samples (Apis mellifera carnica) from Slovenia. Genetic structure and spatial analyses of the microsatellite data sh...

The COLOSS GEI (Genotype-Environment Interactions) Experiment was setup to further our understanding of recent honey bee colony losses. The main objective of the GEI experiment was to understand the effects of environmental factors on the vitality of European honey bee genotypes. This paper aims to describe the genetic background and population all...

The survival and performance of 597 honey bee colonies, representing five subspecies and 16 different genotypes, were comparatively studied in 20 apiaries across Europe. Started in October 2009, 15.7% of the colonies survived without any therapeutic treatment against diseases until spring 2012. The survival duration was strongly affected by environ...

An international collaborative experiment was run from 2009 to 2012 (Costa et al., 2012) with the aim of understanding genotype-environment effects on survival and health status of honey bee colonies headed by queens of different European origins that were tested in various locations under differing environmental conditions. No chemical treatment a...

Adaptation of honey bees to their environment is expressed by the annual development pattern of the colony, the balance with food sources and the host -parasite balance, all of which interact among each other with changes in the environment. In the present study, we analyse the development patterns over a period of two years in colonies belonging t...

Honey bee colonies exhibit a wide range of variation in their behaviour, depending on their genetic origin and environmental factors. The COLOSS Genotype-Environment Interactions Experiment gave us the opportunity to investigate the phenotypic expression of the swarming, defensive and hygienic behaviour of 16 genotypes from five different honey bee...

Honey bee workers were sampled across the Serbian territory during 2009-2010 from mostly non-migratory apiaries to determine the population structure of these bees using morphometric, genetic, and spatial information. A total of 134 bees were sampled, of which 77 were analysed using classical wing morphometrics and 122 bees were successfully analys...

The recognition that the Dark European honey bee, Apis mellifera mellifera, is increasingly threatened in its native range has led to the establishment of conservation programmes and protected areas throughout western Europe. Previous molecular surveys showed that, despite management strategies to preserve the genetic integrity of A. m. mellifera,...

Although knowledge about honey bee geographic and genetic diversity has increased tremendously in recent decades, the adaptation of honey bees to their local environment has not been well studied. The current demand for high economic performance of bee colonies with desirable behavioural characteristics contributes to changing the natural diversity...

Diseases are known to be one of the major contributors to colony losses. Within a Europe-wide experiment on genotype - environment interactions, an initial 621 colonies were set up and maintained from 2009 to 2012. The colonies were monitored to investigate the occurrence and levels of key pathogens. These included the mite Varroa destructor (mites...

Nosema is a microsporidian parasite of the honeybee, which infects the epithelial cells of the gut. In Denmark, honeybee colonies have been selectively bred for the absence of Nosema over decades, resulting in a breeding line that is tolerant toward Nosema infections. As the tolerance toward the Nosema infection is a result of artificial selection,...

Nosema ceranae has been recently introduced into the honeybee Apis mellifera as a novel microsporidian gut parasite. To locate the genetic region involved in N. ceranae infection tolerance, we fed N. ceranae spores to haploid drones of a F1 hybrid queen produced from a cross between a queen of a Nosema resistant bred strain and drones of susceptibl...

Chronic bee paralysis virus (CBPV) is known as a disease of worker honey bees. To investigate pathogenesis of the CBPV on the queen, the sole reproductive individual in a colony, we conducted experiments regarding the susceptibility of queens to CBPV. Results from susceptibility experiment showed a similar disease progress in the queens compared to...

Sacbrood virus (SBV) is the causal agent of a disease of honey bee larvae, resulting in failure to pupate and causing death. The typical clinical symptom of SBV is an accumulation of SBV-rich fluid in swollen sub-cuticular pouches, forming the characteristic fluid-filled sac that gives its name to the disease. Outbreaks of the disease have been rep...