Dirk C de Graaf

• PhD
• Principal Investigator at Ghent University

Asian hornets (Vespa velutina nigrithorax) are an invasive species that have spread across Europe since 2004. As V. velutina largely predate on honeybees, assessing their presence at apiaries would be useful for invasive species control programmes and beekeepers to help protect their hives. At present, hornet monitoring techniques are both costly a...

MaxEnt modeling predicts that 46.4 % of Ethiopia's land mass is currently suitable habitat for Varroa destructor. • The annual mean temperature is the most influential factor (43.2 %) determining V. destructor distribution in Ethiopia. • Cool-humid and sub-humid agroecolog-ical zones are expected to be the most suitable habitats for V. destructor....

The ectoparasite Varroa destructor is a major contributor to the global decline of honeybee colonies (Apis mellifera), especially in the Northern Hemisphere. However, Varroa-resistant honeybee populations have been reported in various regions around the globe, including Europe and Africa. This resistance is primarily attributed to the trait known a...

Highlights • One fifth of a sample of European beekeepers (n = 844) use digital hive monitoring. • Adoption of digital hive monitoring is higher among professional beekeepers. • Observed adoption rates approach the social tipping point for accelerated adoption. • Beekeepers’ personal attitude emerges as the main driver for technology adoption. • So...

Honey bees are rapidly declining, which poses a significant threat to our environment and agriculture industry. These vital insects face a disease complex believed to be caused by a combination of parasites, viruses, pesticides, and nutritional deficiencies. However, the real aetiology is still enigmatic. Due to the conventional analysis methods, w...

While studies on the sublethal effects of chemical residues in beeswax on adult honey bees are increasing, the study protocols assessing the impacts on honey bee brood in realistic conditions still need to be investigated. Moreover, little is known about the residue’s effect on gene expression in honey bee brood. This study reports the effects of c...

In recent years, managed honey bee colonies have been suffering from an increasing number of biotic and abiotic stressors, resulting in numerous losses of colonies worldwide. A pan-European study, EPILOBEE, estimated the colony loss in Belgium to be 32.4% in 2012 and 14.8% in 2013. In the current study, absolute viral loads of four known honey bee...

Simple Summary Increasing honey bee resilience against the parasitic mite Varroa destructor, while respecting sustainability, may be achieved by enriching natural mite resistance traits in the breeding population. Some of these traits are linked to specific variants in the honey bee genome, which can be pinpointed and characterized with high-throug...

Simple Summary Since the mid-20th century, the parasitic Varroa mite has become a major threat for honey bee health worldwide. However, mature female mites are only able to reproduce in the honey bee colony’s brood cells, which are the hexagonal wax cells in which early bee larvae and pupae develop. By abundantly feeding on the larvae and pupae’s f...

The Carniolan honey bee (Apis mellifera carnica) plays an essential role in crop pollination, environment diversity, and the production of honey bee products. However, the health of individual honey bees and their colonies is under pressure due to multiple stressors, including viruses as a significant threat to bees. Monitoring various virus infect...

In 2019, a joint eight-variant model was published in which eight single nucleotide polymorphisms (SNPs) in seven Apis mellifera genes were associated with Varroa destructor drone brood resistance (DBR, i.e. mite non-reproduction in drone brood). As this model was derived from only one Darwinian Black Bee Box colony, it could not directly be applie...

In this work we aim to provide a quantitative method allowing the probing of the physiological status of honeybee colonies by providing them with a gentle, short, external artificial vibrational shockwave, and recording their response. The knock is provided by an external electromagnetic shaker attached to the outer wall of a hive, driven by a comp...

Simple Summary The demand for apiary products in a global market is increasing, while the beekeeping sector still faces multiple challenges, in particular in developing countries. For example, Ethiopia, despite belonging already to world’s top producers of honey and beeswax and having favorable agroclimatic conditions and biodiversity, still has a...

Simple Summary Honey bees are very important for nature and food production. However, beekeepers’ work is continuously challenged by pests, pathogens, pesticides, and other impacts of the environment on their honey bee colonies, and, therefore, they would greatly benefit from up-to-date insights on the health condition of their bees. To disturb tho...

Invasive vectors can induce dramatic changes in disease epidemiology. While viral emergence following geographical range expansion of a vector is well known, the influence a vector can have at the level of the host's pathobiome is less well understood. Taking advantage of the formerly heterogeneous spatial distribution of the ectoparasitic mite Var...

Ce document analyse les coûts financiers et socio des envenimations dans la commune de Djidja

Ce document est une fiche technique qui anayse les potentialités apitouristiques des défférentes régions du Bénin dans le cadre de la diversification du patrimoine touristique du pays

Tourism is the third most crucial socio-economic sector that generates income and employment in the Republic of Benin, where it occupies a prominent place in the country’s development policies. In response to the sustainable development requirements, tourists are worldwide more and more demanding on the quality and diversity of the services they re...

Cette fiche technique tirée des travaux de Amakpe et al (2023) présente étape par étape, la procédure de multiplication végétative naturellle de la plante mellifère et médicinale Combrenum micranthum pour la promotion de l'espèce dans tous les milieux d'utilisation au Bénin. Simple, sûr et efficace en pépinière

Honey bees play an important role in agricultural landscapes by providing pollination services. Throughout the season, colonies increase their population and collect resources from the available flowering plants. Besides internal mechanisms, such as the amount of brood or the availability of bees to perform foraging flights, colonies are also influ...

We provide a culturomics analysis of the cultivable bacterial communities of the crop, midgut and hindgut compartments, as well as the ovaries, of the invasive insect Vespa velutina, along with a cultivation-independent analysis of samples of the same nest through 16S rRNA amplicon sequencing. The Vespa velutina bacterial symbiont community was dom...

Simple Summary Globally, honey bees are exposed to many challenges, such as the Varroa destructor mite and various viruses, which lead to massive losses. It is generally believed that African honey bees are more resilient and better able to cope with these stressors. This study examined some molecular markers that may be associated with this resili...

The beekeeping sector is suffering from the detrimental effects of climate change, both directly and indirectly. Despite numerous studies conducted on this subject, large-scale research incorporating stakeholders' and beekeepers' perspectives has remained elusive. This study aims to bridge this gap by assessing the extent to which stakeholders invo...

Combretum micranthum is a medicinal and melliferous plant from the dry tropical regions where it is threatened with extinction and it urges to develop suitable methods for its sustainable domestication. The challenges of producing seedlings from the seeds of the species make stem cutting, a potential approach for its domestication and this research...

Envenomation is one of the greatest neglected health challenges It hinders and kills rural populations in developing countries and as such deserves particular care. This research attempted to (i) analyze the venomous fauna, their victims, the performance of medical and endogenous care systems in a rural area of Benin and (ii) determine the guiding...

Monitoring virus infections can be an important selection tool in honey bee breeding. A recent study pointed towards an association between the virus-free status of eggs and an increased virus resistance to deformed wing virus (DWV) at the colony level. In this study, eggs from both naturally surviving and traditionally managed colonies from across...

The ‘suppressed in-ovo virus infection’ trait (SOV) was the first trait applied in honey bee breeding programs aimed to increase resilience to virus infections, a major threat for colony survival. By screening drone eggs for viruses, the SOV trait scores the antiviral resistance of queens and its implications for vertical transmission. In this stud...

A key to healthy beekeeping is the Health Status Index (HIS) inspired by EFSA’s Healthy-B toolbox which we will make fully operational, with the active collaboration of beekeepers, by facilitating the coordinated and harmonised flow of data from various sources and by testing and validating each component thoroughly. We envisage a step�by-step expa...

Het afgelopen decennium werden er wereldwijd alarmerend hoge sterftecijfers bij honingbijen geregistreerd. Deze trend is problematisch omdat de bij een cruciale rol speelt als bestuiver in natuurlijke en agrarische ecosystemen. Deze problematiek wordt veroorzaakt door verschillende stressoren met de varroamijt (Varroa destructor) als belangrijkste....

In 1977, a sample of diseased adult honeybees ( Apis mellifera ) from Egypt was found to contain large amounts of a previously unknown virus, Egypt bee virus, which was subsequently shown to be serologically related to deformed wing virus (DWV). By sequencing the original isolate, we demonstrate that Egypt bee virus is in fact a fourth unique, majo...

In the last decade, alarmingly high honeybee mortality rates have been registered. This trend is problematic because honeybees play a crucial role in natural and agricultural ecosystems. These increased mortality rates have several causes with the varroa mite (Varroa destructor) as the most important cause. However, independently of its cause, the...

The honey bee ectoparasite Varroa destructor is considered the major threat to apiculture, as untreated colonies of Apis mellifera usually collapse within a few years. In order to control this mite, many beekeepers rely on a limited number of approved synthetic acaricides, including the pyrethroids tau-fluvalinate and flumethrin. Due to the intensi...

Simple Summary Honey bee colonies collect pollen from plants as a source of nutrients. Diverse diets comprising pollen from many different plant species are beneficial for honey bee colony health, because they contain a greater diversity of nutrients than monofloral diets of one plant species only. Here, we present the results of the COLOSS “CSI Po...

Explaining the reasons for the high honey bee (Apis mellifera) colony loss rate in recent years has become a top global research priority in apicultural and agricultural sciences. Although there are indications of the role played by beekeeping management practices on honey bee health, very little information is currently available. Our study aimed...

Viruses, and in particular the deformed wing virus (DWV), are considered as one of the main antagonists of honey bee health. The ‘suppressed in ovo virus infection’ trait (SOV) described for the first time that control of a virus infection can be achieved from genetically inherited traits and that the virus state of the eggs is indicative for this....

Background The varroa mite is one of the main causes of honey bee mortality. An important mechanism by which honey bees increase their resistance against this mite is the expression of suppressed mite reproduction. This trait describes the physiological inability of mites to produce viable offspring and was found associated with eight genomic varia...

Wild bees are in decline on a local to global scale. The presence of managed honey bees can lead to competition for resources with wild bee species, which has not been investigated so far for human-modified landscapes. In this study we assess if managed honey bee hive density influence nest development (biomass) of bumble bees, an important trait a...

Understanding amateur beekeepers’ perception of risks affecting bee health and mortality is essential to analyse the reasons for adopting or rejecting good management practices. A perception survey on how beekeepers perceive and manage factors related to climate change, Varroa infestation, management practices, and pesticide exposure was designed a...

Twenty-two pesticides and veterinary drugs of which residues were detected in beeswax in Europe were selected according to different criteria. The risk to honey bee health posed by the presence of these residues in wax was assessed based on three exposure scenarios. The first one corresponds to the exposure of larvae following their close contact w...

Background: The varroa mite is one of the main causes of honey bee mortality. An important mechanism by which honey bees increase their resistance against this mite is the expression of suppressed mite reproduction. This trait describes the physiological inability of mites to produce viable offspring and was found associated with eight genomic vari...

Metagenomics studies have accelerated the discovery of novel or divergent viruses of the honey bee. However, most of these studies predominantly focused on RNA viruses, and many suffer from the relatively low abundance of viral nucleic acids in the samples (i.e., compared to that of the host). Here, we explored the virome of the Ethiopian honey bee...

This report (in Dutch) summarizes results and lessons learnt from the citizen science project Vespawatch in Flanders (North Belgium), a project on monitoring the invasion of Vespa velutina using various citizen science groups.

Recent advancements in sequencing technologies and metagenomic studies have increased the knowledge of the virosphere associated with honey bees tremendously. In this study, viral-like particle enrichment and deep sequencing was deployed to detect viral communities in managed Belgian honey bees. A substantial number of previously undescribed diverg...

Honey bees have a sting which allows them to inject venomous substances into the body of an opponent or attacker. As the sting originates from a modified ovipositor, it only occurs in the female insect, and this is a defining feature of the bee species that belong to a subclade of the Hymenoptera called Aculeata. There is considerable interest in b...

Honey bees are under pressure due to abnormal high colony death rates, especially during the winter. The infestation by the Varroa destructor mite and the viruses that this ectoparasite transmits are generally considered as the bees’ most important biological threats. Almost all efforts to remedy this dual infection have so far focused on the contr...

The health of honey bees is threatened by multiple factors, including viruses and parasites. We screened 557 honey bee (Apis mellifera) colonies from 155 beekeepers distributed all over Belgium to determine the prevalence of seven widespread viruses and two parasites (Varroa sp. and Nosema sp.). Deformed wing virus B (DWV-B), black queen cell virus...

This article presents managed honey bee colony loss rates over winter 2018/19 resulting from using the standardised COLOSS questionnaire in 35 countries (31 in Europe). In total, 28,629 beekeepers supplying valid loss data wintered 738,233 colonies, and reported 29,912 (4.1%, 95% confidence interval (CI) 4.0–4.1%) colonies with unsolvable queen pro...

Pesticide and veterinary drug residues are one of the stress factors affecting bee health and mortality. To investigate the occurrence, the concentration and the toxicity risk to bees of pesticide residues in four different types of beeswax (brood comb wax, recycled comb wax, honey comb wax, and cappings wax), 182 samples were collected from apiari...

The European honey bee species (Apis mellifera L.) is under increasing pressure from anthropogenic and other stressors. Winter mortality of entire colonies is generally attributed to biological, environmental, and management conditions. The rates of winter mortality can vary extremely from place to place. A landscape approach is used here to examin...

Honey bees (Apis mellifera) produce an enormous economic value through their pollination activities and play a central role in the biodiversity of entire ecosystems. Recent efforts have revealed the substantial influence that the gut microbiota exert on bee development, food digestion, and homeostasis in general. In this study, deep sequencing was...

The molecular divergence, morphology and pathology of a cryptic gregarine that is related to the bee parasite Apicystis bombi Lipa and Triggiani, 1996 is described. The 18S ribosomal DNA gene sequence of the new gregarine was equally dissimilar to that of A. bombi and the closest related genus Mattesia Naville, 1930, although phylogenetic analysis...

Pages (pp.) 54-69. gronomique du Bénin (BRAB)-Numéro Agricole Durable (DAD)-Août 2019 Le BRAB est en ligne (on line) sur les sites web http://www.slire.net & http://www.inrab.org ISSN sur papier (on hard copy) : 1025-2355 et ISSN en ligne (on line)

Although Braula coeca does not parasitize honey bees, it causes economic impact when its larval stage burrows under the capping of honey combs. We sampled 175 and 195 honey bee colonies between December 2014–September 2015 during the dry and wet seasons respectively from two highland agro-ecological zones of Uganda with the aim of establishing B. c...

In order to assess bee and human exposure to residues of glyphosate-based herbicide (GBH) and its main degradation products aminomethylphosphonic acid (AMPA) and to characterise the risk posed by these substances, we analysed 3 different bee matrices; beebread (N = 81), wax (N = 100) and 10-paired samples of wax/honey collected in 2016/2017 from 37...

Worldwide, the ecto-parasitic mite Varroa destructor has been assigned as an important driver of honey bee (Apis mellifera) colony losses. Unlike the subspecies of European origin, the honey bees in some African countries such as Uganda and Ethiopia may not be as threatened or suffer less from mite-infestations. However, only little is known about...

Cette fiche technique présente les principes, et et conditions de l'alimentation des abeilles mellifères en mileux tropicaux

C'est un document technique qui analyse principes et conditions d'alimentation des abeilles mellifères en apiculture tropicale

To assess the health risk posed by flumethrin residues in beeswax to honeybees and honey consumers, 124 wax samples randomly distributed in Belgium were analysed for flumethrin residues using liquid chromatography/tandem mass spectrometry. The risk posed by flumethrin residues in beeswax to honeybee health was assessed through the calculation of a...

This short article presents loss rates of honey bee colonies over winter 2017/18 from 36 countries, including 33 in Europe, from data collected using the standardized COLOSS questionnaire. The 25,363 beekeepers supplying data passing consistency checks in total wintered 544,879 colonies, and reported 26,379 (4.8%, 95% CI 4.7–5.0%) colonies with uns...

Host-parasite co-evolution history is lacking when parasites switch to novel hosts. This was the case for Western honey bees (Apis mellifera) when the ectoparasitic mite, Varroa destructor, switched hosts from Eastern honey bees (Apis cerana). This mite has since become the most severe biological threat to A. mellifera worldwide. However, some A. m...

In this short note we present comparable loss rates of honey bee colonies during winter 2016/2017 from 27 European countries plus Algeria, Israel and Mexico, obtained with the COLOSS questionnaire. The 14,813 beekeepers providing valid loss data collectively wintered 425,762 colonies, and reported 21,887 (5.1%, 95% confidence interval 5.0–5.3%) colo...

Honeybee (Apis mellifera) venom (HBV) represents an ideal model to study the role of particular venom components in allergic reactions in sensitized individuals as well as in the eusociality of Hymenoptera species. The aim of this study was to further characterize the HBV components C1q-like protein (C1q) and PDGF/VEGF-like factor 1 (PVF1). C1q and...

Globally, honeybees are threatened by human-mediated factors like pests, diseases and pesticides. In this study, 370 honeybee colonies were surveyed for selected invertebrate and vertebrate pests in wet and dry seasons (December 2014 to September 2015). Observations were made on human activities, apiary characteristics, landscape and land use type....

Morphometric characteristics combined with genetic markers are powerful tools used for determining honey bee subspecies. Bees samples collected from 94 established apiaries distributed throughout all of the Republic of Benin were morphometricaly characterized using seven parameters and the COI-COII regions of mitochondrial DNA were sequenced. Based...

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...

Bees are associated with a remarkable diversity of microorganisms, including unicellular parasites, bacteria, fungi, and viruses. The application of next-generation sequencing approaches enables the identification of this rich species composition as well as the discovery of previously unknown associations. Using high-throughput polyadenylated ribon...

The microsporidium Nosema neumanni n. sp., a new parasite of the honeybee Apis mellifera is described based on its ultra-structural and molecular characteristics. Structures resembling microsporidian spores were found by microscopic examination of honeybees from Uganda. Molecular confirmation failed when PCR primers specific for Nosema apis and Nos...

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...

Bees, wasps, and ants possess predatory and/or defensive venoms that contain many toxic compounds. Diverse life cycles of this enormous group of insects implicate a large variability in venom compositions. Several venom compounds have been reported to cause an allergic reaction in humans, suggesting that a good knowledge of the composition of venom...

Keywords: conflict resolution division of labour honeybees patriline reproductive conflict social insects worker policing Cooperation in biological systems is frequently maintained by social enforcement mechanisms, where individually egoistic and group-costly behaviour is mutually suppressed by other group members. One of the best examples in natur...

Pollinator services and the development of beekeeping as a poverty alleviating tool have gained considerable focus in recent years in sub-Saharan Africa. An improved understanding of the pervasive environmental extent of agro-chemical contaminants is critical to the success of beekeeping development and the production of clean hive products. This s...