Stefan Berg - Academia.edu (original) (raw)

Papers by Stefan Berg

Scientific Reports, 2018

Honey bees are increasingly important in the pollination of crops and wild plants. Recent reports... more Honey bees are increasingly important in the pollination of crops and wild plants. Recent reports of the weakening and periodical high losses of managed honey bee colonies have alarmed beekeeper, farmers and scientists. Infestations with the ectoparasitic mite Varroa destructor in combination with its associated viruses have been identified as a crucial driver of these health problems. Although yearly treatments are required to prevent collapses of honey bee colonies, the number of effective acaricides is small and no new active compounds have been registered in the past 25 years. RNAi-based methods were proposed recently as a promising new tool. However, the application of these methods according to published protocols has led to a surprising discovery. Here, we show that the lithium chloride that was used to precipitate RNA and other lithium compounds is highly effective at killing Varroa mites when fed to host bees at low millimolar concentrations. Experiments with caged bees and...

Journal of Apicultural Research, 2014

Journal of Apicultural Research, 2014

Journal of Apicultural Science, Jun 1, 2012

C e c i l i a C o s t a 1 * , R a l p h Büchler 2 * , S t e f a n B e r g 3 * , M a l g o r z a t... more C e c i l i a C o s t a 1 * , R a l p h Büchler 2 * , S t e f a n B e r g 3 * , M a l g o r z a t a B i e n k o w s k a 4 * , M a r i a B o u g a 5 , D r a g a n B u b a l o 6 , L e o n i d a s C h a r i s t o s 7 , Y v e s Le Conte 8 * , M a j a D r a z i c 9 , W i n f r i e d D y r b a 1 0 * , J a n j a F i l l i p i 1 1 , F a n i H a t j i n a 7 * , E v g e n i y a I v a n o v a 1 2 , N i k o l a K e z i c 6 * , H r i s u l a K i p r i j a n o v s k a 1 3 , M i c h a l i s K o k i n i s 1 4 , S e p p o K o r p e l a 1 5

Journal of Apicultural Research, 2014

The survival and performance of 597 honey bee colonies, representing five subspecies and 16 diffe... more 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 environmental factors (apiary effects) and, to a lesser degree, by the genotypes and origin of queens. Varroa was identified as a main cause of losses (38.4%), followed by queen problems (16.9%) and Nosema infection (7.3%). On average, colonies with queens from local origin survived 83 days longer compared to non-local origins (p < 0.001). This result demonstrates strong genotype by environment interactions. Consequently, the conservation of bee diversity and the support of local breeding activities must be prioritised in order to prevent colony losses, to optimize a sustainable productivity and to enable a continuous adaptation to environmental changes. La influencia del origen genético y su interacción con los efectos del medio ambiente en la supervivencia de las colonias de Apis mellifera L. en Europa Resumen La supervivencia y el rendimiento de 597 colonias de abejas, representando cinco subespecies y 16 genotipos distintos, se estudiaron comparativamente en 20 apiarios en Europa. Iniciado en Octubre de 2009, el 15.7% de las colonia sobrevivieron sin ningún tratamiento

Journal of Apicultural Research, 2014

Die Ausbreitung der Asiatischen Hornisse (Vespa velutina) wird seit ihrer Einschleppung nach Fran... more Die Ausbreitung der Asiatischen Hornisse (Vespa velutina) wird seit ihrer Einschleppung nach Frankreich im Jahr 2004, beobachtet. In der Zwischenzeit wurde sie auch in Deutschland nachgewiesen. Zudem wurde der Kleine Beutenkäfer (Aethina tumida) 2014 ebenfalls nach Europa eingeschleppt. Beide Schädlinge können Bienenvölkern großen Schaden zufügen und es ist nur eine Frage der Zeit, bis sie Deutschland (Kleiner Beutenkäfer) oder Bayern (Asiatische Hornisse) erreichen. Daher wurde im Mai 2017 das Projekt "Bee Warned" ins Leben gerufen. Die Ziele des Projektes sind Imker und Veterinäre im Erkennen der zwei vorhergenannten exotischen Schädlinge zu schulen und ein Monitoringsystem für eine frühe Erkennung in der ersten Phase des Auftretens einzurichten. Damit die Monitoring-Imkereien möglichst gleichmäßig verteilt sind, wurde Bayern in Quadrate mit 25 km Kantenlänge eingeteilt. In jedem der 140 Quadrate sollte mindestens ein Monitoring-Imker oder –Imkerin drei Mal jährlich Date...

Apidologie, 2010

The Western honey bee, Apis mellifera, is the most important animal pollinator in agriculture wor... more The Western honey bee, Apis mellifera, is the most important animal pollinator in agriculture worldwide providing more than 90% of the commercial pollination services. Due to the development in agriculture the demands for honey bee pollination are steadily increasing stressing the pollination capacity of the global managed honey bee population. Hence, the long-term decline of managed honey bee hives in Europe and North-America is of great concern and stimulated intensive research into the possible factors presumably causing honey bee colony collapse. We here present a four-year study involving more than 1200 bee colonies from about 120 apiaries which were monitored for the entire study period. Bee samples were collected twice a year to analyze various pathogenic factors including the ectoparasitic mite Varroa destructor, fungi (Nosema spec., Ascosphaera apis), the bacterium Paenibacillus larvae, and several viruses. Data on environmental factors, beekeeping management practice, and pesticides were also collected. All data were statistically analyzed in respect to the overwintering mortality of the colonies. We can demonstrate for several factors that they are significantly related to the observed winter losses of the monitored honey bee colonies: (i) high varroa infestation level, (ii) infection with deformed wing virus (DWV) and acute bee paralysis virus (ABPV) in autumn, (iii) queen age, and (iv) weakness of the colonies in autumn. No effects could be observed for Nosema spec. or pesticides. The implications of these findings will be discussed. colony losses / Varroa / DWV / ABPV / Nosema / pesticides

Journal of Apicultural Research, 2014

Adaptation of honey bees to their environment is expressed by the annual development pattern of t... more 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 to 16 different genotypes and placed in areas grouped within six environmental clusters across Europe. The colonies were maintained with no chemical treatment against varroa mites. The aim of the study was to investigate the presence of genotype-environment interactions and their effects on colony development, which we use in this study as a measure of their vitality. We found that colonies placed in Southern Europe tend to have lower adult bee populations compared to colonies placed in colder conditions, while the brood population tends to be smaller in the North, thus reflecting the shorter longevity of bees in warmer climates and the shorter brood rearing period in the North. We found that both genotype and environment significantly affect colony development, and that specific adaptations exist, especially in terms of adult bee population and overwintering ability.

Journal of Apicultural Research, 2014

Journal of Apicultural Science, 2012

Ethol Ecol Evol, 2007

ABSTRACT Co-evolution between parasites and their host can lead to dramatic changes in the life h... more ABSTRACT Co-evolution between parasites and their host can lead to dramatic changes in the life history of the host species. In this study we tested the male mating success of 31 honeybee (Apis mellifera) colonies infested with the brood parasitic mite Varroa destructor and analysed the consequences of sexual reproduction on colony survival in a closed population on a Mediterranean island. We found that colonies which successfully reproduced via males had a significantly increased mortality during the following season. They also showed a higher investment in the production of drones than unsuccessful ones, while overall colony size was not significantly different. Since honeybee colonies boost their mite population as soon as they start sexual male reproduction, drone production may result in increased mortality. Because this mechanism selects for colonies which produce relatively few or no male sexuals, this change in life history might form an evolutionary constraint for A. mellifera in its co-evolution with the V. destructor mite, as high numbers of males are essential in the highly polyandrous mating system of A. mellifera.

Julius Kuhn Archiv, Oct 2, 2012

Apidologie

Transgenic oilseed rape pollen and its influence on microorganisms in the gut of bees. Le pollen ... more Transgenic oilseed rape pollen and its influence on microorganisms in the gut of bees. Le pollen de colza transgénique et son influence sur les microorganismes de l'intestin des abeilles. Pflanzenschutz, Bioindikatoren, Rückstände Plant protection, bioindicators, residues Protection des plantes, indicateurs biologiques, résidus 22. Einfluss von Völkerführung, Volksentwicklung und Varroa-Befall auf das Auftreten der Varroatose. P. Aumeier, O. Boecking, D. Wittmann Influence of hive management, population dynamics and Varroa destructor infestation on varroatosis. Influence sur la varroose de la gestion des ruchers, de la dynamique des colonies et de l'infestation par Varroa destructor. 23. Varroatose-Krankheitskomplex: gibt es ein Wechselspiel? O. Boecking, P. Aumeier, W. Ritter, D. Wittmann Varroatosis-disease complex: is there any interrelation? Varroose et complexe de maladies : y at -il une corrélation ? 24. Übertragen Varroa-Milben auch Faulbrut (Melissococcus pluton)? G. Kanbar, W. Engels, G. Winkelmann Do Varroa destructor mites transfer European foulbrood (Melissococcus pluton)? Varroa destructor transmet-il aussi la loque européenne (Melissococcus pluton) ? 25. Milben machen Männer müde... Windkanal-Versuche mit Varroa-parasitierten Drohnen. P. Duay, W. Engels Mites can tire men: wind tunnel test with Varroa destructor parasitized drones. Les acariens fatiguent les mâles… Essais dans un tunnel de vol avec des mâles d'abeilles parasités par Varroa destructor. 26. Populationsentwicklung von Varroa destructor bei isoliert aufgestellten Einzelvölkern. M. Renz, P. Rosenkranz Population dynamics of Varroa destructor in isolated bee colonies. La dynamique des populations de Varroa destructor dans des colonies d'abeilles isolées. 27. Flugdauer Varroa destructor befallener Bienenarbeiterinnen (Apis mellifera). J. Kralj, S. Fuchs Flight duration of worker bees (Apis mellifera) infested by Varroa destructor. La durée de vol des ouvrières (Apis mellifera) infestées par Varroa destructor. 28. Reproduktion und Genotyp bei Varroa destructor in Brasilien. C. Garrido, P. Rosenkranz, L.S. Gonçalves Reproduction and genotype of Varroa destructor in Brazil. Reproduction et génotype de Varroa destructor au Brésil. 29. Beziehung zwischen der Inzucht und Varroatoleranzmerkmalen bei Apis mellifera carnica.

Scientific Reports, 2018

Honey bees are increasingly important in the pollination of crops and wild plants. Recent reports... more Honey bees are increasingly important in the pollination of crops and wild plants. Recent reports of the weakening and periodical high losses of managed honey bee colonies have alarmed beekeeper, farmers and scientists. Infestations with the ectoparasitic mite Varroa destructor in combination with its associated viruses have been identified as a crucial driver of these health problems. Although yearly treatments are required to prevent collapses of honey bee colonies, the number of effective acaricides is small and no new active compounds have been registered in the past 25 years. RNAi-based methods were proposed recently as a promising new tool. However, the application of these methods according to published protocols has led to a surprising discovery. Here, we show that the lithium chloride that was used to precipitate RNA and other lithium compounds is highly effective at killing Varroa mites when fed to host bees at low millimolar concentrations. Experiments with caged bees and...

Journal of Apicultural Research, 2014

Journal of Apicultural Research, 2014

Journal of Apicultural Science, Jun 1, 2012

C e c i l i a C o s t a 1 * , R a l p h Büchler 2 * , S t e f a n B e r g 3 * , M a l g o r z a t... more C e c i l i a C o s t a 1 * , R a l p h Büchler 2 * , S t e f a n B e r g 3 * , M a l g o r z a t a B i e n k o w s k a 4 * , M a r i a B o u g a 5 , D r a g a n B u b a l o 6 , L e o n i d a s C h a r i s t o s 7 , Y v e s Le Conte 8 * , M a j a D r a z i c 9 , W i n f r i e d D y r b a 1 0 * , J a n j a F i l l i p i 1 1 , F a n i H a t j i n a 7 * , E v g e n i y a I v a n o v a 1 2 , N i k o l a K e z i c 6 * , H r i s u l a K i p r i j a n o v s k a 1 3 , M i c h a l i s K o k i n i s 1 4 , S e p p o K o r p e l a 1 5

Journal of Apicultural Research, 2014

The survival and performance of 597 honey bee colonies, representing five subspecies and 16 diffe... more 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 environmental factors (apiary effects) and, to a lesser degree, by the genotypes and origin of queens. Varroa was identified as a main cause of losses (38.4%), followed by queen problems (16.9%) and Nosema infection (7.3%). On average, colonies with queens from local origin survived 83 days longer compared to non-local origins (p < 0.001). This result demonstrates strong genotype by environment interactions. Consequently, the conservation of bee diversity and the support of local breeding activities must be prioritised in order to prevent colony losses, to optimize a sustainable productivity and to enable a continuous adaptation to environmental changes. La influencia del origen genético y su interacción con los efectos del medio ambiente en la supervivencia de las colonias de Apis mellifera L. en Europa Resumen La supervivencia y el rendimiento de 597 colonias de abejas, representando cinco subespecies y 16 genotipos distintos, se estudiaron comparativamente en 20 apiarios en Europa. Iniciado en Octubre de 2009, el 15.7% de las colonia sobrevivieron sin ningún tratamiento

Journal of Apicultural Research, 2014

Die Ausbreitung der Asiatischen Hornisse (Vespa velutina) wird seit ihrer Einschleppung nach Fran... more Die Ausbreitung der Asiatischen Hornisse (Vespa velutina) wird seit ihrer Einschleppung nach Frankreich im Jahr 2004, beobachtet. In der Zwischenzeit wurde sie auch in Deutschland nachgewiesen. Zudem wurde der Kleine Beutenkäfer (Aethina tumida) 2014 ebenfalls nach Europa eingeschleppt. Beide Schädlinge können Bienenvölkern großen Schaden zufügen und es ist nur eine Frage der Zeit, bis sie Deutschland (Kleiner Beutenkäfer) oder Bayern (Asiatische Hornisse) erreichen. Daher wurde im Mai 2017 das Projekt "Bee Warned" ins Leben gerufen. Die Ziele des Projektes sind Imker und Veterinäre im Erkennen der zwei vorhergenannten exotischen Schädlinge zu schulen und ein Monitoringsystem für eine frühe Erkennung in der ersten Phase des Auftretens einzurichten. Damit die Monitoring-Imkereien möglichst gleichmäßig verteilt sind, wurde Bayern in Quadrate mit 25 km Kantenlänge eingeteilt. In jedem der 140 Quadrate sollte mindestens ein Monitoring-Imker oder –Imkerin drei Mal jährlich Date...

Apidologie, 2010

The Western honey bee, Apis mellifera, is the most important animal pollinator in agriculture wor... more The Western honey bee, Apis mellifera, is the most important animal pollinator in agriculture worldwide providing more than 90% of the commercial pollination services. Due to the development in agriculture the demands for honey bee pollination are steadily increasing stressing the pollination capacity of the global managed honey bee population. Hence, the long-term decline of managed honey bee hives in Europe and North-America is of great concern and stimulated intensive research into the possible factors presumably causing honey bee colony collapse. We here present a four-year study involving more than 1200 bee colonies from about 120 apiaries which were monitored for the entire study period. Bee samples were collected twice a year to analyze various pathogenic factors including the ectoparasitic mite Varroa destructor, fungi (Nosema spec., Ascosphaera apis), the bacterium Paenibacillus larvae, and several viruses. Data on environmental factors, beekeeping management practice, and pesticides were also collected. All data were statistically analyzed in respect to the overwintering mortality of the colonies. We can demonstrate for several factors that they are significantly related to the observed winter losses of the monitored honey bee colonies: (i) high varroa infestation level, (ii) infection with deformed wing virus (DWV) and acute bee paralysis virus (ABPV) in autumn, (iii) queen age, and (iv) weakness of the colonies in autumn. No effects could be observed for Nosema spec. or pesticides. The implications of these findings will be discussed. colony losses / Varroa / DWV / ABPV / Nosema / pesticides

Journal of Apicultural Research, 2014

Adaptation of honey bees to their environment is expressed by the annual development pattern of t... more 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 to 16 different genotypes and placed in areas grouped within six environmental clusters across Europe. The colonies were maintained with no chemical treatment against varroa mites. The aim of the study was to investigate the presence of genotype-environment interactions and their effects on colony development, which we use in this study as a measure of their vitality. We found that colonies placed in Southern Europe tend to have lower adult bee populations compared to colonies placed in colder conditions, while the brood population tends to be smaller in the North, thus reflecting the shorter longevity of bees in warmer climates and the shorter brood rearing period in the North. We found that both genotype and environment significantly affect colony development, and that specific adaptations exist, especially in terms of adult bee population and overwintering ability.

Journal of Apicultural Research, 2014

Journal of Apicultural Science, 2012

Ethol Ecol Evol, 2007

ABSTRACT Co-evolution between parasites and their host can lead to dramatic changes in the life h... more ABSTRACT Co-evolution between parasites and their host can lead to dramatic changes in the life history of the host species. In this study we tested the male mating success of 31 honeybee (Apis mellifera) colonies infested with the brood parasitic mite Varroa destructor and analysed the consequences of sexual reproduction on colony survival in a closed population on a Mediterranean island. We found that colonies which successfully reproduced via males had a significantly increased mortality during the following season. They also showed a higher investment in the production of drones than unsuccessful ones, while overall colony size was not significantly different. Since honeybee colonies boost their mite population as soon as they start sexual male reproduction, drone production may result in increased mortality. Because this mechanism selects for colonies which produce relatively few or no male sexuals, this change in life history might form an evolutionary constraint for A. mellifera in its co-evolution with the V. destructor mite, as high numbers of males are essential in the highly polyandrous mating system of A. mellifera.

Julius Kuhn Archiv, Oct 2, 2012

Apidologie

Transgenic oilseed rape pollen and its influence on microorganisms in the gut of bees. Le pollen ... more Transgenic oilseed rape pollen and its influence on microorganisms in the gut of bees. Le pollen de colza transgénique et son influence sur les microorganismes de l'intestin des abeilles. Pflanzenschutz, Bioindikatoren, Rückstände Plant protection, bioindicators, residues Protection des plantes, indicateurs biologiques, résidus 22. Einfluss von Völkerführung, Volksentwicklung und Varroa-Befall auf das Auftreten der Varroatose. P. Aumeier, O. Boecking, D. Wittmann Influence of hive management, population dynamics and Varroa destructor infestation on varroatosis. Influence sur la varroose de la gestion des ruchers, de la dynamique des colonies et de l'infestation par Varroa destructor. 23. Varroatose-Krankheitskomplex: gibt es ein Wechselspiel? O. Boecking, P. Aumeier, W. Ritter, D. Wittmann Varroatosis-disease complex: is there any interrelation? Varroose et complexe de maladies : y at -il une corrélation ? 24. Übertragen Varroa-Milben auch Faulbrut (Melissococcus pluton)? G. Kanbar, W. Engels, G. Winkelmann Do Varroa destructor mites transfer European foulbrood (Melissococcus pluton)? Varroa destructor transmet-il aussi la loque européenne (Melissococcus pluton) ? 25. Milben machen Männer müde... Windkanal-Versuche mit Varroa-parasitierten Drohnen. P. Duay, W. Engels Mites can tire men: wind tunnel test with Varroa destructor parasitized drones. Les acariens fatiguent les mâles… Essais dans un tunnel de vol avec des mâles d'abeilles parasités par Varroa destructor. 26. Populationsentwicklung von Varroa destructor bei isoliert aufgestellten Einzelvölkern. M. Renz, P. Rosenkranz Population dynamics of Varroa destructor in isolated bee colonies. La dynamique des populations de Varroa destructor dans des colonies d'abeilles isolées. 27. Flugdauer Varroa destructor befallener Bienenarbeiterinnen (Apis mellifera). J. Kralj, S. Fuchs Flight duration of worker bees (Apis mellifera) infested by Varroa destructor. La durée de vol des ouvrières (Apis mellifera) infestées par Varroa destructor. 28. Reproduktion und Genotyp bei Varroa destructor in Brasilien. C. Garrido, P. Rosenkranz, L.S. Gonçalves Reproduction and genotype of Varroa destructor in Brazil. Reproduction et génotype de Varroa destructor au Brésil. 29. Beziehung zwischen der Inzucht und Varroatoleranzmerkmalen bei Apis mellifera carnica.