A long-term field study on the effects of dietary exposure of clothianidin to varroosis-weakened honey bee colonies.

Clothianidin is a commonly used systemic insecticide in seed treatments. Residues of clothianidin can occur in nectar and pollen as a result of within-plant-translocation. Foraging bees can collect contaminated nectar or pollen. Concerns have been brought forward that exposure to pesticide residues might affect colonies especially if they are weakened by varroosis. However, there are few scientific studies investigating such multiple-stressor scenarios in the context of the entire colony. To close this gapa field trial with 24 colonies was set up. The study design comprised four groups of six colonies each fed with uncontaminated sugar syrup ('C0'), or syrup spiked with 10 µg L-1 clothianidin ('C10'), 50 µg L-1 clothianidin ('C50') or 200 µg L-1 clothianidin ('C200'). C10 represented a residue concentration that may exceptionally occur and therefore a worst-case scenario, the higher dietary concentrations exceed and do not reflect fieldrealistic levels. A substantial load of 8 mites of Varroa destructor per ten gram bees in autumn was adjusted. The colonies were followed up for 328 days. The amount of brood and the strength of each colony were regularly assessed. Colony health, bee mortality, overwintering success, hive weights, and levels of in-hive residues were determined. Varroosis turned out to be the significant key factor for the endpoint colony strength. Clothianidin did not have a statistically significant impact on C0, C10 and C50 colonies. No statistical evidence was found for an interaction between varroosis andexposure to clothianidin.

Immunosuppression in Honeybee Queens by the Neonicotinoids Thiacloprid and Clothianidin.

Queen health is crucial to colony survival of honeybees, since reproduction and colony growth rely solely on the queen. Queen failure is considered a relevant cause of colony losses, yet few data exist concerning effects of environmental stressors on queens. Here we demonstrate for the first time that exposure to field-realistic concentrations of neonicotinoid pesticides can severely affect the immunocompetence of queens of western honeybees (Apis mellifera L.). In young queens exposed to thiacloprid (200 µg/l or 2000 µg/l) or clothianidin (10 µg/l or 50 µg/l), the total hemocyte number and the proportion of active, differentiated hemocytes was significantly reduced. Moreover, functional aspects of the immune defence namely the wound healing/melanisation response, as well as the antimicrobial activity of the hemolymph were impaired. Our results demonstrate that neonicotinoid insecticides can negatively affect the immunocompetence of queens, possibly leading to an impaired disease resistance capacity.

Performance of honey bee colonies under a long-lasting dietary exposure to sublethal concentrations of the neonicotinoid insecticide thiacloprid.

BACKGROUND: Substantial honey bee colony losses have occurred periodically in the last decades. The drivers for these losses are not fully understood. The influence of pests and pathogens are beyond dispute, but in addition, chronic exposure to sublethal concentrations of pesticides has been suggested to affect the performance of honey bee colonies. This study aims to elucidate the potential effects of a chronic exposure to sublethal concentrations (one realistic worst-case concentration) of the neonicotinoid thiacloprid to honey bee colonies in a three year replicated colony feeding study. RESULTS: Thiacloprid did not significantly affect the colony strength. No differences between treatment and control were observed for the mortality of bees, the infestation with the parasitic mite Varroa destructor and the infection levels of viruses. No colony losses occurred during the overwintering seasons. Furthermore, thiacloprid did not influence the constitutive expression of the immunity-related hymenoptaecin gene. However, upregulation of hymenoptaecin expression as a response to bacterial challenge was less pronounced in exposed bees than in control bees. CONCLUSION: Under field conditions, bee colonies are not adversely affected by a long-lasting exposure to sublethal concentrations of thiacloprid. No indications were found that field-realistic and higher doses exerted a biologically significant effect on colony performance. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The neonicotinoids thiacloprid, imidacloprid, and clothianidin affect the immunocompetence of honey bees (Apis mellifera L.).

A strong immune defense is vital for honey bee health and colony survival. This defense can be weakened by environmental factors that may render honey bees more vulnerable to parasites and pathogens. Honey bees are frequently exposed to neonicotinoid pesticides, which are being discussed as one of the stress factors that may lead to colony failure. We investigated the sublethal effects of the neonicotinoids thiacloprid, imidacloprid, and clothianidin on individual immunity, by studying three major aspects of immunocompetence in worker bees: total hemocyte number, encapsulation response, and antimicrobial activity of the hemolymph. In laboratory experiments, we found a strong impact of all three neonicotinoids. Thiacloprid (24h oral exposure, 200 µg/l or 2000 µg/l) and imidacloprid (1 µg/l or 10 µg/l) reduced hemocyte density, encapsulation response, and antimicrobial activity even at field realistic concentrations. Clothianidin had an effect on these immune parameters only at higher than field realistic concentrations (50-200 µg/l). These results suggest that neonicotinoids affect the individual immunocompetence of honey bees, possibly leading to an impaired disease resistance capacity.

Identification of Kashmir bee virus in France using a new RT-PCR method which distinguishes closely related viruses.

A new RT-PCR protocol has been developed, avoiding potential misdiagnosis of Kashmir bee virus (KBV) linked to the use of KBV primers designed originally. The PCR assay validation was realised taking into account the analytical specificity and the PCR detection limit. KBV was detected in a bee sample collected in France from an apparently healthy apiary in 2012. The specificity of the primers was confirmed by sequencing the PCR product. This French sequence clustered into the KBV genotype by phylogenetic analysis, while previous French sequence isolates collected in 2002 belong to the IAPV genotype. These data represent the first detection of KBV in France.

Evaluation of the nutritive value of maize for honey bees.

In modern managed agro-ecosystems, the supply of adequate food from blooming crops is limited to brief periods. During periods of pollen deficiencies, bees are forced to forage on alternative crops, such as maize. However, pollen of maize is believed to be a minor food source for bees as it is thought to be lacking in proteins and essential amino acids. This study was conducted to verify this assumption. In maize, a strikingly low concentration of histidine was found, but the amount of all other essential amino acids was greater than that of mixed pollen. The performance and the immunocompetence of bees consuming a pure maize pollen diet (A) was compared to bees feeding on a polyfloral pollen diet (B) and to bees feeding on an artificial substitute of pollen (C). Consumption of diets A and C were linked to a reduction in brood rearing and lifespan. However, no immunological effects were observed based on two parameters of the humoral immunity.

Multiplex RT-PCR with broad-range primers and an exogenous internal amplification control for the detection of honeybee viruses in bumblebees.

Bumblebees are commercially reared and transported worldwide mainly for pollination of greenhouse tomatoes. Three honeybee viruses have been reported in bumblebees: Acute bee paralysis virus, Kashmir bee virus and Deformed wing virus. We developed a multiplex RT-PCR with primers designed on highly conserved regions of the RNA-dependent RNA polymerase in order to detect a maximum range of viral variants. Rearing facilities and governmental organizations can now thoroughly screen bumblebee colonies with a cost-effective technique with an integrated internal amplification control (IAC) implementable in laboratories that strive for International Organization for Standardization (ISO) certification.

Honey bee viruses.

Viruses are significant threats to the health and well-being of the honey bee, Apis mellifera. To alleviate the threats posed by these invasive organisms, a better understanding of bee viral infections will be of crucial importance in developing effective and environmentally benign disease control strategies. Although knowledge of honey bee viruses has been accumulated considerably in the past three decades, a comprehensive review to compile the various aspects of bee viruses at the molecular level has not been reported. This chapter summarizes recent progress in the understanding of the morphology, genome organization, transmission, epidemiology, and pathogenesis of honey bee viruses as well as their interactions with their honey bee hosts. The future prospects of research of honey bee viruses are also discussed in detail. The chapter has been designed to provide researchers in the field with updated information about honey bee viruses and to serve as a starting point for future research.

[First detection of Kashmir bee virus in Hesse, Germany]. / Erstbefund des Kaschmir-Bienen-Virus in Hessen.

We gathered dead bees of 56 Hessian bee colonies following a sudden collapse during winter 2002/03. Viral RNA was purified from ten dead bees per sample. Kashmir bee virus (KBV) was detected by use of a RT-PCR protocol. 13 samples were positive for KBV. The PCR amplicon was sequenced. A BLAST GenBank search clearly identified the Hessian amplicon as a KBV fragment. Similarities of more than 85% were found. Phylogenetic analysis revealed a close genetic relationship of the Hessian isolate to an isolate from New Zealand. The Northamerican, the Russian and Australian notations listed in GenBank did not cluster round with the Hessian isolate. This is the first documented detection of KBV in Middle Europe.

[Symptomatic Black Queen Cell Virus infection of drone brood in Hessian apiaries]. / Symptomatischer Befall von Drohnenbrut mit dem Black Queen Cell Virus auf hessischen Bienenständen.

The Black Queen Cell Virus (BQCV) can affect brood of the honey bee (Apis mellifera). In general queen cells are endangered showing dark coloured cell walls as typical symptoms. Worker- and dronebrood can be infected by BQCV but normally without clinical symptoms. This paper describes for the first time a symptomatic BQCV-infection of diseased drone brood found on two bee yards in Hessen/Germany in 2001. The drone larvae were seriously damaged and some of them were dead. Samples of the affected brood were tested for BQCV by the PCR detection method. A BQCV specific nucleic acid fragment was found. The PCR product were sequenced and aligned with the relevant GenBank entry. At the nucleic acid level as well as at the deduced protein level the isolate showed a high similarity with the south african isolate noted in GenBank.